Prior to his political career, Mangabeira was an astronomy professor at the Federal University of Bahia.

He was repeatedly jailed in the 1930s for conspiring against the dictatorship, and then forced into exile in 1938, which he spent first in Europe and then in New York City.

[5][6] While in New York, he managed to financially supported himself and his family by working for Reader's Digest magazine to translate issues from English into Portuguese.

[8] When American General Dwight Eisenhower visited Brazil in 1946, Mangabeira greeted him in Rio de Janeiro, and a famous photograph taken by Ibrahim Sued appeared to show Mangabeira kissing Eisenhower's hand in greeting; the image provoked intense public debate about Brazil's relationship to the United States.

[10] In part as a consequence of his repeated exiles and imprisonments, Mangabeira spent most of his life with very little money, and "lacked, at the time of his death, the means to pay for his own burial.