In a career spanning over four decades from the eighties, his roles included ministering, teaching, directing and managing largescale human resources in educational, goodwill-promoting and literary organisations with a pan-Indian presence.
While at the London University, Chacko studied under the Old Testament Scholar, Ronald E. Clements and later published his thesis in book form in 2002 with the title, Liberation And Service Of God.
[3] Mani Chacko was taken as faculty member on Serampore College, Serampore (West Bengal) from academic year 1983–1984 onwards, where he began to teach Old Testament, also providing his guidance to Scholars studying in North India Institute of Post Graduate Theological Studies.
In 2001,[8] Chacko was appointed as Principal of the Seminary, a post which he held until 2006 when he moved over to the Ecumenical Christian Centre, Bangalore to take up its Directorship.
He was installed on 13 September 2011 at the CSI-St. Mark's Cathedral, Bangalore by the Bible Society of India Trust Association led by its President Navamani Elia Peter in the presence of a host of clergy, G. Dyvasirvadam, John S. Sadananda, G. D. V. Prasad, Robert R. Cunville, Joseph Mar Thoma, Ignatius Paul Pinto and others.