The historic event of the reunion of His Grace Archbishop Geevarghese Mar Ivanios with the Catholic Church took place on 20 September 1930.  Archbishop Mar Ivanios and Mar Theophilos along with Fr. John Kuzhinapurath OIC, Deacon Alexander OIC and Mr. Chacko Kilileth, members of the Malankara Orthodox Church, made their profession of faith on the very same day and entered into full communion with the Catholic Church before His Excellency Aloysius Maria Benziger OCD, Bishop of the Diocese of Quilon (Kollam), who was specially delegated by the Holy See.
            His Grace Mar Ivanios initiated the work of the re-union movement under the guidence of the Holy See, especialy in the light of the Apostolic Decree Magnum Nobis  of His Holiness Pope Pius XI. His Grace made his visit to Rome in1932 and His Holiness Pope Pius XI invested him with the Sacred Pallium. The Holy Father, Pope Pius XI through the Apostolic Constitution Christo Pastorum Principi of 11 June 1932, established the Syro-Malankara Hierarchy and erected the Archieparchy of Trivandrum as the Metropolitan See with the suffragan Eparchy of Tiruvalla. The territorial boundary of the Archieparchy of Trivandrum was established from Kanyakumari, the southernmost part of India to the north up to river Pampa, to the Western Ghats in the east and to the Arabian Sea in the west.
            The Metropolitan Eparchy of Trivandrum, with its head quarters in Trivandrum, was inaugurated on 11 May 1933 and His Grace Mar Ivanios was enthroned as its first Metropolitan-Archbishop at the provisional Cathedral, dedicated to the Mother of God, at Palayam, Trivandrum.  Having made the Profession of  faith before the august assembly of the Bishops, priests and laymen and amidst the acclamations of ‘Oxios’ (a customary hymn for the occasion) Archbishop Mar Ivanios was enthroned as the Metropolitan Archbishop of Trivandrum and the Hierarchical Head of the Syro-Malankara Catholic Church. The Apostolic Constitution was executed by His Excellency Aloysius Maria Benziger,the Bishop of Quilon. On the following day His Grace Mar Ivanios celebrated the solemn Qurbono in the same Pro-Cathedral, concelebrated by Bishop Jacob Mar Theophilos, the Bishop of Tiruvalla.  His Grace Mar  Augustine Kandathil, the Archbishop of Ernakulam, His Grace Mar James Kalassery, the Archbishop of Changanassery, His Excellency Mar Alexander Choolaparambil, the Bishop of Kottayam, Rt. Rev. Joseph Pulikottil Remban and Rt. Rev. Philipose Cheppad Remban were present on the occasion.
            As part of the evangelising ministry of the southern regions of Thiru-kochi including parts now bordering Tamil Nadu, Archbishop Mar Ivanios himself initiated evangelisation ministry at Marthandom.  Later, with the blessings of Archbishop Mar Ivanios, Rt. Rev. Msgr. Joseph Kuzhinjalil founded the missionary congregation of the Daughters of Mary in 1938 at Marthandom in Kanyakumari District.  Through the great zeal of these missionaries, the mission of the Syro-Malankara Catholic Church spread to the southern regions of Kerala and Tamil Nadu.
            Mar Ivanios worked relentlessly for the building up of the Syro-Malankara Catholic Church. Through his travels abroad (Rome and other European countries, America and Australia) he spread the message of ecclesial communion and the awareness of the mission of the Syro-Malankara Catholic Church in the Universal Church. After a period of 22 years of strenuous hectic task of organizing and administering the Syro-Malankara Catholic Church he fell ill for more than a year. Archbishop Mar Ivanios ordained Benedict Mar Gregorios as his Auxiliary and as the Titular Bishop of Anterdos on 29 January 1953. After a period of heroic leadership for the Syro-Malankara Catholic Church, and for the Metropolitan Eparchy of Trivandrum, Archbishop Mar Ivanios was called to eternal rest on 15 July 1953 and was entombed at St.Mary’s Cathedral.   
            Upon the demise of His Grace Mar Ivanios, His Excellency Benedict Mar Gregorios was appointed the Apostolic Administrator of the Metropolitan Eparchy of Trivandrum by the Holy See. On 27 January 1955, His Holiness Pope Pius XII appointed him the Metropolitan Archbishop of Trivandrum thereby also as the Head of the Syro- Malankara Catholic Church. Under the spiritual leadership, pastoral guidance and social commitment of Archbishop Benedict Mar Gregorios, the Church began to flourish in its various dimensions throughout the States in South India, North America and other European Countries.
The Syro-Malankara Catholic Church was making rapid growth. Most Rev. Paulos Mar Philoxenos, the Metropolitan of the Malabar Independent Church, reunited with the Syro-Malankara Catholic Church on 28 August 1977 and was appointed Episcopal Vicar of the Metropolitan Eparchy of Trivandrum.
            His Excellency Most Rev. Lawrence Mar Ephraem was appointed Auxiliary to the Metropolitan Archbishop of Trivandrum and Titular Bishop of Barkuso on 6 November 1980 and was ordained Bishop by His Benedict Mar Gregorios on 27 December 1980 at Kottayam during the Golden Jubilee celebration of the Reunion Movement.
            The Syro- Malankara Catholic Church was fortunate to welcome His Holiness Pope John Paul II of happy memory on 8 February 1986 at St. Mary’s Cathedral, Pattom, Trivandrum. His Holiness was accorded a cordial reception by the entire Church, the Hierachy and the represantatives of the Clergy, the Religious and the Laity. The Supreme Pontiff was garlanded at the entrance of the Cathedral by His Grace Benedict Mar Gregorios, the Metropolitan Archbishop and was received  in to the Cathedral with the liturgical reception by the Bishops of the Syro- Malankara Catholic Church. His Holiness prayed at the sanctuary. After the welcome speech of His Grace Benedict Mar Gregorios, the Holy Father gave His speech. In His Speech the Holy Father praised the unity endeavors of Mar Ivanios “ In coming to this cathedral, I pay honour to the memory of Archbishop Mar Ivanios who is buried here. Among the many apostolic endeavors of his zealous pastor of souls, none was more dear to him than the promotion of unity among christians.” After the visit to St. Mary’s Cathedral, His Holiness addressed the whole Catholic community from Trivandrum and the neighbouring districts at Shankumukham beach. In His memorable speech at Shankumukham the Holy Father praised the heroic leadership of Mar Ivanios of happy memory and the ecclesial significance of the Syro-Malankara Reunion Movement (L’Osservatore Romano, Feb.17, 1986).
            His Eminence Cardinal Lourdusamy, the Prefect of the Congregation for the Oriental Churches, visited the Metropolitan Eparchy of Trivandrum on 19 August 1987.
            After an eventful leadership of 41 years His Grace the Metropolitan Archbishop Benedict Mar Gregorios was called to eternal rest on 10 October 1994 and was buried at St. Mary’s Cathedral. His Excellency Most  Rev. Lawrence Mar Ephraem, the Proto-Syncellus, was elected the Administrator of the Metropolitan Eparchy of Trivandrum. As per the appointment of Holy See, on 14 December 1995 His Excellency Most Rev. Cyril Mar Baselios, the Bishop of Bathery, was enthroned the Metropolitan Archbishop of Trivandrum and the Head of the Church at the St. Mary’s Cathedral, Trivandrum. His Grace received Sacred Pallium from the Holy Father Pope John Paul II on 9 January 1996 in Vatican.
His Eminence Achille Cardinal Silvestrini, Prefect of the Congregation for the Oriental Churches, visited the Metropolitan Eparchy of Trivandrum, on 12, & 13 of February 1996.
            His Eminence Josef Cardinal Tomko, Prefect of the Congregation for the Evangelization of Peoples was received in the Archbishop’s House on 2 November 1996.
            Upon the request of His Grace Cyril Mar Baselios, bifurcating the Metropolitan Eparchy of Trivandrum, His Holiness Pope John Paul II erected the Eparchy of Marthandom on 16 December 1996 and Most Rev. Lawrence Mar Ephrem was appointed as its first Bishop. His Grace Cyril Mar Baselios officiated the Installation of His Excellency Mar Ephraem at Christuraja Cathedral, Marthandom on 23 January 1997. The territorial boundary of the Eparchy of Marthandom extends to Kanyakumari in the south, Kalikavilai in the west, Kavalkinar in the north and Kumarapuram in the east.
            The new extension of the Archbishop’s House ‘Thirusannidhi’ was blessed by Metropolitan Archbishop Most Rev. Cyril Mar Baselios on 11 and 12 March 1998.
            On 16 April 1998, the Holy See appointed Most Rev. Joshua Mar Ignathios as the Auxiliary Bishop for the Archieparchy of Trivandrum. He was ordained Bishop on 29 June 1998 at Mar Ivanios Nagar, Nalanchira, by Metropolitan Archbishop His Grace Cyril Mar Baselios. 
            His Excellency Most Rev. Paulos Mar Philoxenos, Episcopal Vicar of the Metropolitan Eparchy of Trivandrum passed away on 3 November 1998, and was buried in St. John’s Cathedral, Tiruvalla. .
On 18 June 2001 Most Rev. Isaac Mar Cleemis was appointed by the Holy See as the Apostolic Visitor of North America and Europe and the Auxiliary Bishop of Trivandrum and as the titular Bishop of Chayal.  His Episcopal Ordination took place on 15 August 2001 at St. Mary’s Malankara Catholic Church, Thirumoolapuram, Tiruvalla. His Grace Cyril Mar Baselios, the Metropolitan Archbishop was the principal consecrator.
            The Holy See on 11 September 2003 appointed Bishop Isaac Mar Cleemis, as the Bishop of Tiruvalla when Bishop Geevarghese Mar Timotheos gave resignation due to super-annuation (on 29 March 2003). Most Rev. Isaac Mar Cleemis was installed Bishop of Tiruvalla on 2 October 2003.
            Most Rev. Joseph Mar Thomas was appointed by Holy Father Pope John Paul II as Apostolic Visitor to North America and Europe and Auxiliary Bishop of Trivandrum and as the Titular Bishop of Silcilibbensis on 5 January 2005. He was ordained Bishop on 19 February 2005 at St. Mary’s Cathedral, Trivandrum, by His Grace Cyril Mar Baselios, the Metropolitan Archbishop.
            On 10 February 2005,  a day engraved in golden letters in the history of the Syro-Malankara Catholic Church, His Holiness Pope John Paul II of venerable memory raised this Church to the status of a Major Archiepiscopal Church and appointed the then Metropolitan Archbishop as Major Archbishop of the Syro-Malankara Catholic Church by the Papal Bull Ab ipso Sancto Thoma  (PopeJohn Paul II, Apostolic Bull, Ab ipso Sancto Thoma, Prot. No. 570.809, February 10, 2005, Malankara, 1 (2005) 1, p. 12). This was the crowning event of all the ecclesial communion endeavors since 1653. Thus the Syro-Malankara Catholic Church obtained the Synodal hierarchical structure with Major Archbishop as the “father and head” (pater et caput) of the Church exercising Patriarchal powers with the Synod of Bishops. In accordance with the provisions of the CCEO and the tradition of the Malankara Church, which has its roots in the Syro-Antiochene tradition, the Major Archbishop is the “Catholicos” of the Syro-Malankara Catholic Church, who with the Holy Episcopal Synod exercises Patriarchal powers envisaged in the CCEO (Pope Pius XII, Motu proprio, Cleri sanctitati, AAS 49 (1957) 430-603, c. 335).  In complete concordance with this tradition, the pater et caput of the Syro-Malankara Catholic Major Archiepiscopal Church assumed the title ‘Catholicos’ along with the title Major Archbishop. The announcement was officiated by His Grace Pedro Lopez Quintana, the Apostolic Nuncio  at St. Mary’s Cathedral, Pattom in the presence of all Bishops of the Syro-Malankara Catholic Church and a large number of clergy and faithful.
            The Enthronement of Major Archbishop-Catholicos Moran Mor Cyril Baselios, as the Father and Head of the Syro-Malankara Catholic Major Archiepiscopal Church and Major Archbishop of Trivandrum was held at St.Mary’s Cathedral on 14 May 2005. His Eminence Ignace Cardinal Mousa Daoud, the Prefect of the Congregation for the Oriental Churches and the Patriarch Emeritus of the Syrian Catholic Church of Antioch presided over the liturgy of enthronement. A large number of Bishops, dignitaries, clergy, religious and lay people participated in the functions.
            The Platinum Jubilee of the Reunion Movement and the Year of the Eucharist were celebrated jointly at Mar Ivanios Nagar, Punnamoodu, Mavelikara on 19, 20, 21 September 2005. His Grace Pedro Lopez Quintana, the Apostolic Nuncio in India, Shri Bhaironsingh Shekhawat, the Vice-President of India, and Sri Oommen Chandy, the Chief Minister of Kerala, participated in the celebrations.
            As per the decision of the Holy Episcopal Synod of the Syro-Malankara Catholic Church, and with the assent of the Holy See, His Beatitude Moran Mor Cyril Baselios Catholicos, the Major Archbishop-Catholicos, bifurcated the Major Archieparchy of Trivandrum, and established  the new Eparchy of Mavelikara on 1 January 2007 (Decree, Prot. No. 1/2007). His Excellency Most Rev. Joshua Mar Ignathios, the Auxiliary Bishop of Trivandrum was transferred and appointed (Decree, Prot. No. 2/2007) as the first Bishop of Mavelikara, by His Beatitude Cyril Baselios. The Eparchy of Mavelikara comprises of the presbyteral districts of Mavelikara and Kollam and parts of the presbyteral districts of Chengannur and Adoor. Most Rev. Joshua Mar Ignathios was installed in office at St. Mary’s Church, Puthiakavu on 16 February 2007. 
            As per the decision of the Second Ordinary Holy Episcopal Synod of the Syro-Malankara Catholic Church, which was convoked on 6-7 December 2006 and the ministerial titles of Ramban and Corepiscopo which were in vogue were revived in the Church and to honour a few priests for their meritorious service in the Church. Moran Mor Cyril Baselios Catholicos conferred these titles on ten priests on 17 January, 2007 at St. Mary’s Cathedral, Pattom.
            His Beatitude Moran Mor Cyril Baselios, the first Major Archbishop-Catholicos of the Syro-Malankara Catholic Church passed away on 18 January 2007 and was entombed at St. Mary’s Cathedral, Pattom, Trivandrum on 20 January 2007. On 18 January 2007, Most Rev. Geevarghese Mar Divannasios, the Bishop of Bathery assumed the office of the Administrator of the Syro-Malankara Catholic Church and of the Major Archieparchy of Trivandrum as per CCEO c. 127.
            The members of the Holy Episcopal Syro-Malankara Catholic Major Archiepiscopal Church assembled for the Synod of Election for the first time in the history of the Syro- Malankara Catholic Church on 8 February 2007. On 10 February 2007, after getting the confirmation from the Holy Father Pope Benedict XVI (Decree, No. 13.695/07), the Administrator of the Syro- Malankara Catholic Church announced the election of His Grace Most Rev. Isaac Mar Cleemis, the then Metropolitan Archbishop of Tiruvalla as the new Major Archbishop-Catholicos and the Major Archbishop of Trivandrum. As per the tradition of the Malankara Church, the new Major Archbishop-Catholicos assumed the official name Baselios (along with his episcopal name Cleemis). This was the first election of the Head of an Oriental Catholic Church in India.
            Moran Mor Baselios Cleemis was enthroned as the Second Major Archbishop-Catholicos of the Syro-Malankara Catholic Church and the Major Archbishop of Trivandrum on 5 March 2007 at St. Mary’s Cathedral, Pattom. His installation service was officiated by Most Rev. Geevarghese Mar Divannasios, the Synodal Administrator of the Church. A large number of ecclesiastical and political dignitaries including His Eminence Cardinal Telesphore Toppo (President of the CBCI), His Eminence Cardinal Varkey Vithayathil (Major Archbishop of the Syro-Malabar Church) and Shri. V. S. Achuthanandan (the Chief Minister of Kerala), His Grace Oswald Gracious (Archbishop of Bombay), Official representatives of the Congregation for the Oriental Churches, a large number of Bishops, Priests, Religious, lay faithful and social and political leaders participated in the Enthronement ceremony and public meeting.
            During the 54th Anniversary of the Commemoration of Archbishop Mar Ivanios, His Beatitude Moran Mor Baselios, the Major Archbishop-Catholicos proclaimed Mar Ivanios as Servant of God at St. Mary’s Cathedral, Pattom on 14 July 2007.
            The Tomb of the venerable prelates in St. Mary’s Cathedral was renovated and extended in July 2008. His Beatitude Moran Mor Baselios Cleemis Catholicos blessed the tomb chapel on 5th July 2008. The sanctuary of St. Mary’s Cathedral was renovated and portico was extended to the Cathedral in November 2008. His Beatitude blessed the renovated sanctuary and the portico on November 8, 2008.
            The Platinum Jubilee of the Major Archieparchy of Trivandrum (1933-2008) was celebrated in a meaningful way during 2007-2008. Renewal conventions were held in every ecclesiastical district. 75 houses were built and given to the poor families of the Major Archdiocese. Many charity schemes were launched in parishes and districts. The Jubilee was formally concluded with the visit of His Eminence Leonardo Cardinal Sandri, the Prefect of the Congregation for the Oriental Churches on 10 November 2008. His Eminence was received at St.Mary’s Cathedral, by the Holy Episcopal Synod. During the Holy Mass, the Cardinal Prefect delivered the Jubilee Message and imparted the Blessing of the Holy Father.
            Upon the request of His Beatitude Moran Mor Baselios Cleemis, Major Archbishop Catholicos, the Supreme Pontiff Pope Benedict XVI, elevated St. Mary Queen of Peace Church, Palayam to the title and dignity of a Minor Basilica with all its rights and liturgical privileges on 13 October, 2008, as a souvenir of the Platinum Jubilee of the Major Archieparchy of Trivandrum (2007-2008). The formal announcement of the Basilica was made by His Eminence Leonardo Cardinal Sandri, the Prefect of the Congregation for the Oriental Churches during his visit on 10 November 2008. The church was elevated to the status of Basilica through a solemn liturgical ceremony by His Beatitude Moran Mor Baselios Cleemis, Major Archbishop Catholicos, on 7 December 2008. 
            From 20-26 September 2009, His Beatitude Moran Mor Ignace Yousuf III Younan, the Patriarch of the Syrian Catholic Church of Antioch and a Delegation from the same Church visited the Major Archieparchy of Trivandrum. His Beatitude the Patriarch was the chief guest at the 79th Reunion Day Celebrations on 19-21 September, 2009.
            As per the decision of the Holy Episcopal Synod of the Syro-Malankara Catholic Church and having consulted the Apostolic See of Rome, His Beatitude Moran Mor Baselios Cleemis, Major Archbishop-Catholicos, erected the Eparchy of Pathanamthitta bifurcating the Major Archieparchy of Trivandrum on 25 January 2010. The official declaration was made on the same day by His Beatitude the Major Archbishop-Catholicos at St.Mary’s Cathedral. The territory of the Eparchy of Pathanamthitta consists of four ecclesiastical districts-Pathanamthitta, Konni, Ranni-Perunadu, Pandalam and the parishes of Anandapally, Angadickal, Chandanapally, Pongaldy and Thatta of the eccelsiatical district of Adoor. His Beatitude transferred His Excellency Yoohanon Mar Chrysostom from the Eparchy of Marthandom and appointed him to the new Eparchy of Pathanamthitta as its first Bishop. The new Eparchy of Pathanamthitta was inaugurated and its first Eparch was His Excellency Most Rev. Yoohanon Mar Chrysostom was installed by His Beatitude Moran Mor Baselios Cleemis Major Archbishop-Catholicos on 20 March 2010. Inauguration ceremony was conducted at Cyril Baselios Catholicos Nagar (Muncipal Stadium, Pathanamthitta) and the installation took place at Sacred Heart Malankara Catholic Church, Mylapra.
            Having been elected by the Holy Episcopal Synod of the Syro-Malankara Catholic Church and with the assent of His Holiness Pope Benedict XIV, Most Rev. Dr.Samuel Mar Irenios has been appointed by the Major Archbishop Catholicos as the Auxiliary Bishop of Trivandrum. Most Rev. Dr. Samuel Mar Irenios was ordained Bishop (along with Mar Paulos, Mar Anthonios and Mar Stephanos) by His Beatitude Moran Mor Baselios Cleemis on 13 March 2010 at Mar Ivanios Vidyanagar, Nalanchira Trivandrum. His Beatitude Gregorios III Laham, the Patriarch of the Greek Melkite Catholic Church and a Delegation from the same Church participated in the Episcopal Ordination. His Beatitude Patriarch Gregorios III Laham was the chief guest. The Major Archieparchy of Trivandrum hosted the 80th Reunion Day Celebrations. His Beatitude blessed the Newly built Samannuaya Pastoral Centre in Cathedral Campus on 20th September 2010. During the 80th Re-union day Celebrations at St. Mary’s Cathedral, Pattom, Most Rev. Dr. Thomas Mar Eusebius, the newly appointed Exarch of USA and Apostolic Visitor for Canada and Europe was ordained a Bishop by His Beatitude Moran Mor Baselios Cleemis