In 1985 Mongella became Vice-Chairperson to the World Conference to Review and Appraise the achievements of the UN Decade for Women. In 1989 Mongella was Tanzanian representative to the commission on the Status of Women. From 1990 to 1993 she was a member of the trustee to United Nations International Research and Training Institute for Advancement of Women (INSTRAW).
From 1991 to 1992 President Mongella was Tanzanian High Commissioner to India, in 1995 she was UN Assistant Secretary General and Secretary General, Fourth World Conference on Women on Women in Beijing, China, from 1996 to 1997 Mrs. 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 Member of Advisory Group to Director General UNESCO for the follow-up of the Beijing Conference in Africa.
In 1998 she became a member of the OAU sitting on the Women Committee for Peace and Development, In 1999 she was a member of the “Council of the Future”, UNESCO, Paris, France, in 2000 she was a Member of the Tanzanian Parliament Ukerewe Constituency. In 2002 she was a member of the OAU’s High Level Advisory Panel of Eminent Persons. In 2002 Mongella was a member of the Regional Reproduction Health Task Force for the World Health Organization’s African Region, she was also leader of the OAU Election Observer Team to the Zimbabwean Presidential Election.