Kumar replaced Arvind Panagariya, an Indian-American economist who left the think tank yesterday to return to academia.
Kumar was a senior fellow at the Centre for Policy Research (CPR). He holds a DPhil in economics from Oxford and a PhD from Lucknow University.
Earlier, he had also served as Secretary General of industry association Ficci.
He was a member of the National Security Advisory Board between 2006 and 2008.
Kumar had also served as the chief economist of the Confederation of Indian Industries (CII) and held senior positions in the Asian Development Bank, the Indian Ministry of Industries, and the Ministry of Finance.
Noted economist Rajiv Kumar on Friday took over as the vice-chairman of government think tank Niti Aayog.