Bustamante y Rivero was born in Arequipa and received his early education there. He received his Law Degree from the Universidad de San Agustin and his Ph.D. from the Universidad de San Antonio Abad del Cuzco in Cuzco. After a distinguished career as a teacher and legal scholar, Bustamante y Rivero became interested in politics. He began this new career by serving as a diplomat, representing Peru in various countries in the Americas.
He ran for President in 1945 as a candidate for the Frente Democratico Nacional, a moderate, left-of-center party that aligned itself with Victor Raul Haya de la Torre's APRA party. Opposing him was the Union Nacional Democrata candidate, General Eloy G. Ureta. Bustamante y Rivero handily won the relatively honest election.
As President, Bustamante y Rivero hoped to create a more democratic governement by limiting the power of the military and the oligarchy. Conflict soon arose, however, between the President and Haya de la Torre. Without the support of the APRA party Bustamante y Rivero found his presidency severely limited. Postwar economic problems and strife caused by strong labor unions led to a military coup on October 29, 1948. General Manuel A. Odria became the new President.
Bustamante y Rivero was exiled to Argentina. He finally returned to Peru in 1955. In 1960 he was elected a member of the International Court of Justice in The Hague and served as its President between 1967 and 1969.