He entered military school in 1918 in Porto Alegre and ultimately graduated from the Rcalango Military School in Rio de Janeiro.
He moved up the military hierarchy, attaining the rank of general in 1961.
When General Artur Costa e Silva became president in 1967, he appointed Médici to direct the Servido Nacional de Inteligencia (SNI). which is equivalent to the American Central Intelligence Agency except that it also functions inside Brazil. Then, with the death of President Costa e Silva in August 1969, the army resolved that General Médici would be his successor. On October 25, 1969, the Brazilian Congress carried out the orders of the army, voting 239 for Médici, with 76 abstentions.