[3] He was born in the province of Cartago, son of Nicolás Oreamuno and Adelfia Flores.
[3] His father was Minister of State, president of the Central American Court of Justice and president of the Supreme Court of Justice of Costa Rica, and his brother José Rafael Oreamuno Flores was ambassador of Costa Rica in the United States.
[3] He studied at the National Institute of Honduras, at the Liceo de Costa Rica and at the Lafayette Lyceum in Weston, Pennsylvania, United States.
[3] He later went to the Jefferson Medical College at the University of Pennsylvania where he graduated with honors in 1929, obtaining the therapeutic medal for the best exam among 122 students.
He was also a councilor of the Municipal Council of Limón and deputy, and then served as vice president of Costa Rica in the administration of Otilio Ulate Blanco.