Bouton played in Major League Baseball (MLB) as a pitcher for the New York Yankees, Seattle Pilots, Houston Astros, and Atlanta Braves between 1962 and 1978.

Bouton played college baseball at Western Michigan University, before signing his first professional contract with the Yankees.

Bouton authored the 1970 baseball book Ball Four, which was a combination diary of his 1969 season and memoir of his years with the Yankees, Pilots, and Astros.

In summer leagues, Bouton did not throw particularly hard, but he got batters out by mixing conventional pitches with the knuckleball that he had experimented with since childhood.

(Bouton later explained that he had been assigned the number in 1962 when he was promoted to the Yankees, and wanted to keep it as a reminder of how close he had come to not making the ball club.

[5] He did not play in the Yankees' 1962 World Series victory over the San Francisco Giants, although he had originally been slated to start Game 7.

[5] In Game 3 of the 1963 World Series, Don Drysdale of the Los Angeles Dodgers pitched a three-hit shutout in a 1–0 victory, while Bouton gave up just four hits in seven innings for the Yankees.

[9] In October 1968, Bouton joined a committee of American sportsmen who traveled to the 1968 Summer Olympics, in Mexico City, to protest the involvement of apartheid South Africa.

The Pilots scored six in the top of the 11th inning to earn him the win, even though other Seattle relievers gave five runs back in the bottom of the 11th.

[5] Around 1968, sportswriter Leonard Shecter, who had befriended Bouton during his time with the Yankees, approached him with the idea of writing a season-long diary.

The diary also followed Bouton during his two-week stint with the triple-A Vancouver Mounties in April, and after his trade to the Houston Astros in late August.

[4] Ball Four was not the first baseball diary (Cincinnati Reds pitcher Jim Brosnan had written two such books), but it became more widely known and discussed than its predecessors.

The book made Bouton unpopular with many players, coaches, and officials on other teams as well; he was informally blacklisted from baseball.

Bouton's writings about Mickey Mantle's lifestyle were most notorious, though they comprise few pages of Ball Four and much of the material was complimentary.

After a handful of unsatisfactory appearances, Bouton left baseball to become a local sports anchor for New York station WABC-TV, as part of Eyewitness News; he later held the same job for WCBS-TV.

Bouton also became an actor, playing the part of Terry Lennox in Robert Altman's The Long Goodbye (1973), plus the lead role of Jim Barton in the 1976 CBS television series Ball Four, which was loosely adapted from the book.

[4] He skipped the 1976 season to work on the TV series, but he returned to the diamond in 1977 when Bill Veeck signed him to a minor league contract with the Chicago White Sox.

After a successful season with the Double-A Savannah Braves of the Southern League, he was called up to join Atlanta's rotation in September, and compiled a 1–3 record with a 4.97 ERA in five starts.

His most recent book is Foul Ball, a non-fiction account of his attempt to save Wahconah Park, a historic minor league baseball stadium in Pittsfield, Massachusetts.

[4] Although Bouton had never been officially declared persona non grata by the Yankees or any other team as a result of Ball Four's revelations, he was excluded from most baseball-related functions, including Old-Timers' Games.

On July 25, 1998, Bouton, sporting his familiar number 56, received a standing ovation when he took the mound at Yankee Stadium.