She arranged for her son to work for a millinery shop, delivering hats to well-to-do women. She instructed her son that, if asked his name, to reply simply "Joseph," so as to avoid drawing attention to his ethnic background. Both parents were aware that entry to the higher levels of Boston society dictated that Kennedy mix with those outside his Irish community. They sent their son to Catholic schools for his early education. When he was a bit older, however, he attended Boston Latin School and Harvard University, to be educated with Boston's elite Protestant families.

Although he made some friends at Harvard—especially among the few Irish students there—and was popular with young Irish women, Kennedy never was accepted by a majority of the students. Anti-Irish, anti-Catholic sentiment was strong. One friend warned Kennedy to be very careful in his behavior because Boston Brahmins were watching for any sign that would justify their prejudices. Kennedy's determination to ingratiate himself with the socially prominent Protestants was viewed by some as disagreeable and pretentious. He was never invited to join any of Harvard's better clubs. Friends attested to what they felt was one of Kennedy's more admirable qualities: his adherence to the tenets of his religious upbringing. His Catholic faith was important to him and he attended mass regularly. On one occasion, he even hired a buggy so that all of his friends could ride with him to church.

Kennedy was financially shrewd. He showed an entrepreneurial spirit and an appreciation for money at an early age. Kennedy held a number of jobs as a youngster, including candy vendor, newspaper hawker, and play producer. He also performed jobs for Orthodox Jews, whose faith prohibited them from working on their holy days. During his student days at Harvard, he and a friend bought a bus and began operating sightseeing tours. Kennedy negotiated with another tour operator to share working hours. He was successful at this, earning $5,000 over the course of several summers.

In 1914, two years after his graduation, Kennedy accepted a job as president of Columbia Trust Company Bank. At 25 years of age, he was the youngest bank president in the United States. During that same year, he married Rose Fitzgerald, daughter of Boston's mayor. Kennedy and Rose bought a small home in Brookline, Massachusetts, and started their family. In all, they had nine children: Joseph Jr., John (Jack), Rosemary, Kathleen, Eunice, Patricia, Robert (Bobby), Jean, and Edward (Ted). Several of his children went on to develop distinguished political careers, including two U.S. senators and one U.S. president.

Kennedy supported his large family through numerous successful business ventures. He joined an investment banking firm, bought a chain of New England movie theaters, gained control of a film production company, bought and sold many properties in New York, invested in the stock market, and controlled a franchise on Scotch whiskey and British gin. All of these ventures proved lucrative. He may have earned as much as $5 million in three years from his motion picture work. He earned $8.5 million when he sold the alcohol franchise, which he had purchased for $118,000 13 years earlier. He always made a substantial profit on the properties he bought and sold.

Kennedy's career as a motion picture executive earned him kudos from some observers. He was wise enough not to tamper with a company that already was profitable. In 1926, Kennedy's company FBO produced 50 films. In Hollywood, Kennedy became friends with many well-known actors, Gloria Swanson among them. He became her adviser, consultant, and lover. Swanson named her adopted son after Kennedy. Their relationship lasted several years, but was broken off abruptly, according to Swanson, because she "questioned his judgment" and "he did not like to be questioned."

Although his work as a motion picture executive meant that he frequently was away from his wife and children for long periods of time, Kennedy's interest in and concern for his children remained constant. The children lined up every Sunday to talk with him when he called—in part because their mother insisted on it. Kennedy apparently was happy to talk about his children with his friends in Hollywood; when Joe Jr. had measles, Kennedy told actor Tom Mix about it. Mix sent a telegram to Joe Jr., in which he described his own bout with measles.

Kennedy was concerned about the physical and emotional welfare of his children, too. When his son Jack became ill with scarlet fever, Kennedy spent several days in church praying for his son's recovery. When Robert was of school age, Kennedy complimented him on his efforts to distinguish himself from his two successful, older brothers.

Kennedy's own political involvement began in 1932, when he supported the Democratic presidential nomination of Franklin Delano Roosevelt. He worked as campaign contributor, lender, and fundraiser. In return, President Roosevelt rewarded him with the position of first chairman of the Securities & Exchange Commission, a decision that was not popular in some circles. Still, Kennedy did a thorough and honest job. Despite his wish to become secretary of the treasury, Roosevelt appointed him chairman of the Maritime Commission. Kennedy eventually resigned from the post, tired of dealing with unions and ship-owners. In 1938, Kennedy was appointed ambassador to England. During this sensitive period just prior to World War II, Kennedy made a number of unfortunate mistakes. He was an isolationist, and gave speeches that implied agreement with policies designed to appease Hitler. He announced plans to resettle 600,000 German Jews in other parts of the world—a strategy he had not discussed with President Roosevelt. There also was speculation in some newspapers that Kennedy was thinking of a run for the Presidency in 1940—speculation that irritated Roosevelt, although Roosevelt may have planted the story. Amidst mounting pressure, Kennedy was forced to resign his post in 1940.

Kennedy's life was fraught with tragedy during the 1940s. His eldest son, Joseph, Jr., was killed in action during World War II. His favourite daughter, Kathleen, was killed in a plane crash four years after the death of her husband. His son, Jack, was seriously wounded when his boat was attacked by the Japanese.

After World War II, Kennedy concentrated his efforts on getting his sons elected to political office. He began by working on Jack's campaign for representative in the 11th District of Massachusetts. Kennedy was a quiet but effective campaigner. He contacted every powerful person he knew to assist him with votes and campaign contributions. The tactic (and his personal $50,000 contribution) proved successful. Kennedy employed the same successful strategy in 1952, when Jack ran for the state Senate.

Kennedy's next project—getting his son elected as the first Roman Catholic president of the United States—was launched in the late 1950s. His tactics caused considerable controversy during his son's run for the presidency. Kennedy was accused of influencing delegates at the National Democratic Convention and of buying the nomination for his son. Jack himself once observed "Dad is a financial genius all right, but in politics, he is something else." Kennedy distanced himself from his son during the period prior to and during the nomination process, and did not return to Massachusetts until the election took place. His wife, Rose explained: "He has been a controversial figure all of his life and he thinks it's easier for his sons if he doesn't appear on the scene." Jack Kennedy won the presidential election in 1960, fulfilling his father's dream. But Kennedy's reaction was modest: "I have a strong idea that there is no other success for a father and a mother except to feel that they have made some contributions to the development of their children."

Despite suffering a stroke in 1961, Kennedy remained active and interested in the lives of his grown children. However, tragedy continued to plague his last years. His son Jack was assassinated in 1963, before completing his first term as president. His son, Robert, was assassinated in 1968, while campaigning for the Democratic presidential nomination. His youngest son, Ted, was involved in a scandal with a young woman who drowned while in his company.

Kennedy bore his sorrows with stoicism and courage until his death on November 19, 1969, at Hyannis Port, Massachusetts.