[2] His association with global environmental issues has included participation in the UNEP Session of a Special Character: Ten Years after Stockholm (Nairobi; 1982); contribution to the drafting of the 1990 London Amendments to the Montreal Protocol on Substances that Deplete the Ozone Layer, Convention on Biological Diversity, UN Framework Convention on Climate Change, Rio Declaration on Environment and Development, Statement of Principles on Forests, and Agenda 21; and participation in the UN Conference on Environment and Development (Rio de Janeiro; 1992).

[3][4] He was a member of the UNEP group of legal experts to examine the concept of "Common Concern of Mankind" in relation to global environmental issues.

[5] He was Counsellor (Information) at the Indian Embassy, Moscow, from 1993 to 1996, returning to the Ministry of External Affairs, New Delhi, as Director/Joint Secretary and guided India's foreign relations with 22 Central and Eastern European countries, including Russia.

Based on leaked American diplomatic cables, it was reported that Ajai Malhotra was posted to the UN Mission, New York to balance the anti-US decisions taken by Nirupam Sen, then Permanent Representative of India, to the UN.

[10] He participated in the negotiations leading to the setting up of the UN Democracy Fund, the UN Peacebuilding Commission and the UN Human Rights Council.

Since April 2014 he is a Distinguished Fellow & Senior Adviser (Climate Change) at The Energy and Resources Institute, New Delhi.

[32] On 29 September 2017, he was elected by secret ballot to the Advisory Committee of the United Nations Human Rights Council, Geneva.

[33] On 7 October 2020, he was re-elected by acclamation to the Advisory Committee of the United Nations Human Rights Council, Geneva.

[34] On 15 February 2021, he was elected the Chairperson of the Advisory Committee of the United Nations Human Rights Council, Geneva, the first Indian to hold this position.