Born in Niterói, RJ, Mauro Vieira graduated in Law from the Federal Fluminense University (1973) and in Diplomacy from the Rio Branco Institute (1974), in addition to receiving an honorary doctorate in Letters from Georgetown University, Washington DC (2014).

At the Ministry of Foreign Affairs, Ambassador Vieira served as Coordinator of International Acts; Advisor to the Secretary-General; Advisor to the Minister of Foreign Affairs; Chief of Staff of the Secretary-General; and Chief of Staff of the Minister of Foreign Affairs.

Ambassador Vieira also worked at the Ministry of Science and Technology as Deputy Secretary-General of Science and Technology, and at the Ministry of Social Security and Welfare as National Secretary of Administration of the Social Security Institute.

Abroad, he served as Second Secretary at the Brazilian Embassy in Washington D.C. (1978-1982); at Brazil's Permanent Mission to the Latin American Integration Association (ALADI) in Montevideo (1982-1985) as First Secretary; at the Brazilian Embassy in Mexico City (1990-1992) as Counselor; and at the Brazilian Embassy in Paris (1995-1999) as Minister Counselor.

He was Ambassador of Brazil to Argentina (2004-2010); Ambassador of Brazil to the United States of America (2010-2015); Permanent Representative of Brazil to the United Nations in New York (2016-2020); and Ambassador of Brazil to Croatia (2020-2022). He served as Brazil's Minister of Foreign Affairs from 2015 to 2016.

He was appointed by President Luiz Inácio Lula da Silva to serve as Brazil's Minister of Foreign Affairs starting January 1, 2023.