La Motta grew up in a Bronx slum and turned to boxing while in jail. His first professional bout was in 1941, and on February 5, 1943, he gained national recognition by handing Sugar Ray Robinson (Robinson, Sugar Ray) his first defeat. This victory came in the second of six famous bouts between the two fighters, the rest of which La Motta lost.

After a seven-month suspension for deliberately losing a fight, La Motta returned to contend for the middleweight title. On June 16, 1949, he defeated Marcel Cerdan in Detroit for the world middleweight championship. He successfully defended the title two times the following year (on July 12 against Tiberio Mitri and September 13 against Laurent Dauthuille) before losing in Chicago to Robinson on February 14, 1951, in their final matchup. La Motta retired from the ring in 1954 with 83 wins (30 by knockout), 19 losses, and 4 draws. His autobiography, Raging Bull (1970), was made into a movie, directed by Martin Scorsese (Scorsese, Martin) and starring Robert DeNiro as La Motta, in 1980.