From 1990 to 1993 she was a Member of the Trustee to the United Nations International Research and Training Institute for the Advancement of Women (INSTRAW).

From 1996 to 1997, Mongella was UN Under-Secretary and Special Envoy to the Secretary General of the United Nations on Women's Issues and Development.

In 1996 she was a Member of the Advisory Group to the Director General UNESCO for the follow-up of the Beijing Conference in Africa, South of the Sahara.

In 1996 she was a member of the board for both The Hunger Project in New York City, and the UN University in Tokyo, Japan.

In 1997 Mongella was Senior Advisor to the Executive Secretary of the Economic Commission for Africa on Gender Issues.

[6] She was designated Chairperson of the International Advisory Board of the African Press Organization (APO) in February 2008.