He was born in Milwaukee, Wisconsin, the second son of a truck salesman. At the beginning of World War I he left school to enlist in the Navy, but remained in Norfolk Navy Yard, Virginia throughout the war. Afterwards he attended Ripon College where he appeared in a play entitled, The Truth, and decided on acting as a career. In the early 1920s he attended the Academy of Dramatic Arts in New York. He played minor stock parts, and supported himself with jobs as bellhop, salesman, and janitor.
In 1923 he married Louise Treadwell, and they had two children, John and Louise (Susie). In 1930, director John Ford saw him in the play, The Last Mile and signed him to do Up the River for Fox Pictures. Shortly after that he and his family moved to Hollywood, where he made over 35 films in 5 years. In 1935 he signed with MGM and won the Oscar for best actor two years in a row for Captains Courageous (1937) and Boys Town (1938). He was nominated for San Francisco (1936), Father of the Bride (1950), Bad Day at Black rock (1955), The Old Man and the Sea (1958), Inherit the Wind (1960), Judgment at Nuremberg (1961), and Guess Who's Coming to Dinner (1967).
In 1941 he began a relationship with Katharine Hepburn. Though estranged from his wife, Louise, he was a devout Catholic and never divorced. He and Hepburn continued to have a relationship for the remainder of his life, and made nine films together.
Although Tracy was an alcoholic most of his adult life, it never seemed to affect his career. Thirty years after his death, Tracy is still considered by many to be the most skillful actor of his time. He could portray the hero, the villain, or the comedian, and make the audience believe he truly was the character he played. A few weeks after making his last movie, Guess Who's Coming to Dinner (1967), with Hepburn, he died from a heart attack. He is interred in Forest Lawn Memorial Park Cemetery, Glendale, California.