[3] His father, Thomas Mathai, was a senior faculty member at the National Defence Academy.

Ranjan Mathai is a 1974 batch Indian Foreign Service Officer.He joined the IFS after completing post graduate studies in political science at the University of Poona.

He has served in Indian Embassies in Vienna, Colombo, Washington, Tehran and Brussels.

As Joint Secretary (BSM) in the Ministry of External Affairs in New Delhi (January 1995 to February 1998), he headed the Division dealing with India's relations with Bangladesh, Sri Lanka, Myanmar and Maldives.

He held the post of Deputy High Commissioner of India to the UK in London from August 2005 to January 2007.