Hoffa was born in Brazil, Indiana, on February 14, 1913, to Indiana natives John and Viola (née Riddle) Hoffa. His paternal ancestors were partially Pennsylvania Dutch. His father died in 1920 when Hoffa was seven years old, and the family moved to Detroit in 1924, where Hoffa was raised and lived the rest of his life. Hoffa left school at age 14 and began full-time manual labor to help support his family.
Hoffa began union organizational work at the grassroots level through his employment as a teenager with a grocery chain, which paid substandard wages and offered poor working conditions with minimal job security. The workers were displeased with this situation and tried to organize a union to better their lot. Although Hoffa was young, his bravery and approachability in this role impressed fellow workers, and he rose to a leadership position. By 1932, after defiantly refusing to work for an abusive shift foreman, who inspired Hoffa's long career of organizing workers, he left the grocery chain, in part because of his union activities, and Hoffa was then invited to become an organizer with the Local 299 of the Teamsters in Detroit.
He married Josephine Poszywak in 1936, and in 1939 paid $6,900 for a modest home at 16154 Robson Street in northwest Detroit. The couple had two children: a daughter, Barbara Ann, and a son, James. The Hoffa family later had a summer property at Lake Orion, Michigan, north of Detroit.
The Teamsters union, founded in 1903, had only 75,000 members in 1933. As a result of Hoffa's work with other union leaders to consolidate local union trucker groups into regional sections and then into one gigantic national body—work that Hoffa ultimately completed over a period of two decades—membership grew to 170,000 members by 1936. Three years later, there were 420,000; and the number grew steadily during World War II and through the post-war boom to top a million members by 1951.
The Teamsters organized truck drivers and warehousemen, first throughout the Midwest, and then nationwide. Hoffa played a major role in the union's skillful use of "quickie strikes", secondary boycotts, and other means of leveraging union strength at one company, to then move to organize workers, and finally to win contract demands at other companies. This process, which took several years from the early 1930s, eventually brought the Teamsters to a position of being one of the most powerful unions in the United States.
However, trucking unions in that era were heavily influenced, and in many cases controlled by, elements of organized crime. For Hoffa to unify and expand trucking union groups, he had to make accommodations and arrangements with many gangsters, beginning in the Detroit area. Organized crime influence on the IBT would expand as the union itself grew
Hoffa took over the presidency of the Teamsters in 1958, at the convention in Miami Beach, Florida
Hoffa had first faced major criminal investigations in 1957, as a result of the John Little McClellan Senate Labor Subcommittee's work. He avoided conviction for several years, but when John F. Kennedy was elected president in 1960, he appointed his younger brother Robert F. Kennedy as Attorney General. Robert Kennedy had been frustrated in earlier attempts to convict Hoffa, while working as counsel to the McClellan Subcommittee. As Attorney General from 1961, Robert Kennedy pursued the strongest attack on organized crime that the country had ever seen, and he carried on with a so-called 'Get Hoffa' squad of prosecutors and investigators.