Gwynn played in Major League Baseball (MLB) for the Milwaukee Brewers, San Diego Padres, Los Angeles Dodgers, and the Philadelphia Phillies.

[6] Towards the end of the 2006 campaign, Gwynn received more playing time, replacing Brady Clark in the lineup.

Gwynn pinch-hit for Bill Hall against his dad's former team, and dramatically tied the game with a triple.

The Padres would go on to lose the game as well as the season finale on the next day, opening the door for the Colorado Rockies to force a one-game playoff with San Diego.

Gwynn was optioned to the Nashville Sounds of the Triple-A Pacific Coast League on May 25, 2008, but recalled after rosters expanded on September 1.

[8] Gwynn was informed of the trade by a phone call from his father, who played his entire career with the Padres.

[12] At the end of spring training, it was announced that Gwynn had made the opening day roster to start the 2014 season, which culminated a "long road" back to the major leagues.

[13] He was the Phillies' opening day starter in left field (Domonic Brown, the projected starter in left field, started at designated hitter as the Phillies opened the season on the road against the Texas Rangers), and batted in the ninth position.

[18] He later signed a minor league contract with the Phillies on August 3 with an assignment to their Triple-A affiliate, the Lehigh Valley IronPigs.

[26][27] Gwynn and his wife Alyse Mallek have four children; three daughters Makayla, Jordan and Leighton and a son, Anthony Keith III.