Hart then coached baseball at William R. Boone High School in Orlando, Florida before joining the Orioles organization in 1982 as a minor league manager. He managed in their minor league organization for six seasons before joining the major league team as third base coach in 1988.
Cleveland Indians
In 1989, John Hart joined the Cleveland Indians as a special assignment scout, then later replaced Doc Edwards as manager for the final 19 games of the regular season. For the next two seasons, Hart served as director of baseball operations for the club. In September 1991, John Hart replaced Hank Peters as general manager and executive vice president of the Indians. During the next ten years, the Indians were 870–681 under Hart. They won six of the seven possible American League Central division titles, which was introduced for the 1994 strike shortened season with appearances in the World Series in 1995 and 1997. Hart built the team's core through the draft, successful scouting and trades. He signed young players before the arbitration process got underway and thus enticed veteran players to stay with the team.
Texas Rangers
At the beginning of the 2001 season, Hart announced it would be his last season as general manager of the Indians. After the season, Hart stayed true to his word and assistant GM Mark Shapiro took over as general manager on November 1. But, rather than take another position with the club or retire, Hart instead took the general manager position which had opened up with the Texas Rangers after the departure of Doug Melvin. On July 21, 2004 the Rangers announced a contract extension for Hart for a guaranteed two more years and an annual mutual option to extend the contract each year thereafter. In addition, the contract stipulated that once it was terminated by either side, it automatically converted to a five-year agreement for Hart to serve as senior advisor to the owner. Just over a year after agreeing to the extension, on October 4, 2005, Hart stepped down as general manager and was replaced by Jon Daniels. Hart then became a senior advisor to Daniels. During his four years as general manager, the Rangers compiled a record of 311–337, never advancing to the playoffs. After other teams showed interest in hiring Hart as their general manager during the 2005 off-season, the Rangers extended his senior advisor contract for three more years. He would serve in that post through 2013. In return, he agreed not to consider any other GM positions with rival clubs.
Atlanta Braves
Soon after his Rangers contract expired, the Atlanta Braves announced Hart had signed with the organization as senior advisor for baseball operations, similar to the position Hart held with the Rangers. Hart and long-time Braves executive John Schuerholz had been friends since long before the Braves and Indians met in the 1995 World Series. On September 22, 2014, Hart was named as the Braves interim general manager after the Braves released general manager Frank Wren. On October 23, 2014, the Braves promoted Hart to president of baseball operations. The team, at the time stuck in the lower reaches of the National League East Division, was in the midst of a "reset" that saw them significantly strengthen their young pitching talent. But the rebuild came at a cost. Major League Baseball began to investigate the club's practices in signing amateur players from international markets. The probe resulted in the resignation and subsequent lifetime ban of Hart's subordinate, general manager John Coppolella, and the one-year suspension of the club's scouting director. Hart was not directly implicated in nor sanctioned for the scandal, but he resigned in its wake on November 17, 2017. The following season,, saw the Braves improve significantly on the field, winning 90 games to capture the division championship under their new management team.
Personal life
Hart and his wife Sandi have been married since 1970.
