Ainge played basketball at Brigham Young University, after which he was selected, in 1977, in the baseball draft, by the MLB's Toronto Blue Jays. He made it to the majors with the Blue Jays in 1979, but was able to amass only modest numbers for that team. In 1981, after receiving the John Wooden award as college basketball player of the year, Ainge was chosen in the NBA draft by the Boston Celtics, who had to buy out his contract from the Blue Jays, after enduring a legal battle over the rights to Ainge's contract. Not everything went right for Ainge in basketball at first: according to Larry Bird in his autobiography, Drive, Celtics players used to make fun of Ainge's initial shooting percentage, some suggesting that his batting avegare of .220 was better than his shooting average on the basketball courts. But Ainge became one of the important pieces of the team that won the NBA title in 1984 and 1986, and a major helper of the middle to late 1980s Celtics teams. In 1989, Ainge was traded to the Sacramento Kings for young center Joe Kleine, whom the Celtics saw as a possible substitute to the aging Robert Parish. Despite Ainge's leadership, the Kings could not make it to the playoffs. In 1990, Ainge was traded to the Portland Trail Blazers, whom he helped reach the NBA Finals, only to lose to the Chicago Bulls in six games. He tied a record in this series: On June 5, he scored nine points in overtime to tie the NBA playoffs' all-time record for most points in an overtime during a playoff game. The Phoenix Suns, a team that had been looking for a new identity, were inaugurating a new home (America West Arena), a new coach (Paul Westphal) a new uniform and a new superstar (Charles Barkley) when they signed free agent Ainge before the 1992-1993 NBA season, figuring that his playoff experience would help the team during the playoffs. Ainge responded by scoring 11.8 points per game as the Suns went 62-20 that year, only to lose to the Bulls, also in six games.
Ainge retired after the 1994-1995 season. While a player of the Suns, he opened a national chain of hat stores, The Hat Club, which he still presides. He has worked at a number of charity organizations, and he has held a number of jobs since retiring, including head coach both of the Suns and Trail Blazers, broadcaster for TNT, and, from 2003 on, executive director of basketball operations for the Celtics.
Also, in an early 1990s episode of Married...with Children, light mockery was made at Ainge's expense: At an all-star basketball game that The Bundys attended, the public announcer said Welcome to the game of the NBA stars and Danny Ainge!
Ainge, a second baseman with the Blue Jays, hit the aforementioned .220 in his baseball career, with 2 home runs. As a basketball player, he became the second man ever to hit 900 or more three-point shots in the NBA (he made 1,002 three point shots), and he scored 11,964 points for an average of 11.5 points per game, 2,768 rebounds for an average of 2.7, and 4,199 assists, for a total of 4.0 per game.
Ainge currently makes Gilbert, Arizona his off-season home, and he lives with his wife Michelle. He has six kids.