His parents were Manuel Bustamante y Barreda, a lawyer and district attorney in Arequipa, and Victoria de Rivero y Romero.

Bustamante reached political maturity as the author of the manifesto which launched the 1930 coup that ousted President Augusto B. Leguía.

He soon earned the trust of Leguía's successor, Luis Miguel Sánchez Cerro, and began his new career in 1934 by serving as a diplomat, representing Peru as Peruvian Minister to Bolivia (1934–1938, 1942–1945) and Uruguay (1939–1942).

[3] During his first seven days as president, Bustamante restored press freedom and full civil rights and freed all political prisoners.

In October 1948, rebel sailors and officers seized five warships, locked up or shot their commanders, sent landing parties ashore under cover of a ragged bombardment.

Under the President's orders, government troops occupied the APRA headquarters, seized the plant of its newspaper, La Tribuna, and arrested several prominent Apristas.

In 1969, due to his recognition as an international jurist, the Organization of American States designated Bustamante as a mediator in the border conflict between El Salvador and Honduras known as the Football War, which ended peacefully after a peace treaty was signed on October 30, 1980, in Lima, Peru.