He completed his training for priesthood under the guidance of Thoma Mar Dionysius and Baselios Augen, Catholicos of the East.

Geevarghese II Catholicos ordained him to the order of quroyo (reader deacon) on 11 March 1942 at Karapuzha Mar Gregorios Chapel.

He was ordained a full deacon on 22 May 1947 at Thiruvalla Bethany Aramana Chapel and priest on 25 January 1950 at Pathanapuram Mount Tabor Dayara.

On 16 May 1965, Catholicos of the East Moran Mar Baselios Augen I tonsured him Ramban (monk) at Mount Tabor Dayara.

The Malankara Syrian Christian Association which convened at Kottayam M. D. Seminary on 28 December 1965 and elected him to the office of Metropolitan along with four others priests, following the ancient tradition of, selecting bishops from the monastic ranks.

Due to old age, the current Catholicos, Baselios Marthoma Mathews II, decided to abdicate the throne in 2005.

Didymos I had, as a priest, attended the consecration of holy Myron (anointing oil) officiated by Baselios Geevarghese II in 1951.

As the Catholicos of the East, Didymos I himself officiated in the consecration of holy Myron at Devalokam Catholicate Palace on 5 April 2009.

After his enthronement, Didymos I visited the Holy Land and met the Coptic Pope Shenouda III and exchanged fraternal greetings.

During the incumbency of Didymos I, the prominent prelates who visited Malankara Orthodox Church include Supreme Catholicos of Armenia Karekin II, Ethiopian Patriarch Abune Paulos and Armenian Catholicos of Cilicia Aram I. Didymos I abdicated the throne on 31 October 2010, at the age of 89.