He was 94.
Didymus I stepped down as head of the Kerala-based church in 2010 on the grounds of poor health but continued to be the supreme spiritual head of the community.
He was born in Tiruvalla. Side by side theological studies, he also took a masters degree in English literature and had taught in schools and colleges before raised as a Metropolitan of the church.
He took over as the supreme head of the church in 2005 and was elevated as Catholicos of the East.