Díaz-Balart served as Majority Leader of the Cuban House of Representatives and Deputy Secretary of Interior (1952–1954) during the dictatorship of Fulgencio Batista.
In 1955, Díaz-Balart gave a speech before the Cuban House of Representatives in opposition to the amnesty granted to his former brother-in-law, Fidel Castro, for his involvement in the 1953 attack on the Moncada Barracks (disputed).
Díaz-Balart was elected senator in 1958, but was unable to take office due to Fidel Castro's rise to power on January 1, 1959.
[1] Díaz-Balart founded La Rosa Blanca (The White Rose), the first anti-Castro organization, in January 1959.
[citation needed] Díaz-Balart died on May 6, 2005, in his Key Biscayne, Florida, home after a battle with leukemia.