According to the popular belief, the Marth Mariam Valiyapally at Kothamangalam (St. Mary's Cathedral) was founded in the 4th century by a few Syriac Christian families who migrated from Paravur and Angamali. Among the later Christian inhabitants of the place included a few Syrian Knanaites who eventually intermingled with the local Christian community. (Knanaites are those Syrian Orthodox Christians who migrated to Malabar from the Syrian province of Roman Empire in AD 345, under the leadership 'Thomas of Cana'/'Knai Thoma' and Mor Joseph Metropolitan).

There is also a view that this church was established in AD 1340 by four Syriac Christian merchants who bought the entire land at Kothamangalam from a local chief for commodity trading with the nearby state of Tamilnadu. According to this story, Kothamangalam became a major commercial centre from this period onwards.

The Marth Mariam church at Kothamangalam, commonly known as 'VALIYAPALLY' (Big church) is the oldest of all the churches in the region. The famous Marthoma Cheriapally (Small church) at Kothamangalam, founded  by the 18 families that separated from the old church (Valiyapally) in 1455, is located at a very short distance from Valiyapally. Both these churches are situated in nearby hilltops.

The altars in the Martha Mariam church are dedicated to the Mother of God, Geevarghese Sahdo (St.George), St.John the Baptist, Apostles St.Peter & St.Paul and St.Thomas. The most important festivals of the church are celebrated on 10 February and 15 August. A small portion of the soonoro of St.Mary, rediscovered at the Syrian Orthodox Church at Homs in 1953 by Patriarch Mor Aphrem I, was established in this church in 1980 by the diocesan Metropolitan Thomas Mor Dionysius (the present Catholicos of Malankara, Aboon Mor Baselios Thomas).

Inside view of the MarthMariam Jacobite Syrian Church (Kothamangalam Valiyapally)

The Font containing The Holy Girdle (Soonoro) of our Mother of God

All the five Patriarchs of Antioch who had visited Malankara in the last two centuries came to this church as well. Last of these Patriarchal visits was that of His Holiness Ignatius Zakka I Iwas in 1982. It was during this historical visit the Holy Patriarch had ordained an assistant metropolitan for the diocese by name Mor Severios Abraham, at the Kothamangalam Cheriapally.

As per the biography of St. Gregorios of Malankara (Chathuruthy Kochu Thirumeni) written by Mookencheril Paily Varkey in 1903, Palakunnath Mathews Mor Athanasius ordained the saintly Gregorios Thirumeni as Korooyo in this church in 1858. (There is another view that St. Gregorios entered the first stage of deacon hood at Karingachira St. George Jacobite Syrian church).

From 1974 to 1997, the building adjacent to the Valiyapally was the bishop's residence of the diocesan Metropolitan. A technical institute owned by the Marth Mariam Valiyapally is also situated very near to the church. Various spiritual organizations like Marth Mariam Vanitha Samajam, Sunday School, Prayer groups, Youth Association etc. have branches in this church. There is one chapel and 5 shrines under the Kothamangalam Valiyapally.