John Mabry played Division I baseball for three seasons at West Chester University where he was the prototype of the versatile outfielder/infielder known for his defensive prowess and hitting.

His success at WCU was noticed by Major League Baseball scouts, and he was drafted by the St. Louis Cardinals in the sixth round of the 1991 MLB draft. He made his MLB debut with the Cardinals three years later on April 23, 1994 against the Houston Astros when he singled and scored an RBI while playing right field. With his MLB promotion he became one of only ten WCU players to play in the Major Leagues and his fourteen years of playing time is the longest tenure of any WCU baseball professional.

In his first full MLB year (1995), playing mostly first base and the outfield, he batted .307 with an OBP of .347 and finished fourth in Rookie of the Year balloting. The following year he hit .297 and helped the Cardinals reach the National League Championship series where they lost in seven games to the Atlanta Braves. During the year he became one of only sixteen Cardinals to hit for the cycle.

Mabry played eight seasons with the Cardinals during three stops with the franchise. He also played for the Seattle Mariners, San Diego Padres, Florida Marlins, Philadelphia Phillies, Oakland Athletics, Chicago Cubs, and Colorado Rockies. In the latter part of his career he transitioned from a starter to a highly regarded bench player. Mabry was an important member of the 2004 Tony LaRussa managed Cardinals. John helped them reach the post-season by hitting 13 home runs as a part-time player in the regular season. The Cardinals were swept in the 2004 World Series as the Boston Red Sox captured their first World Series since 1918. In 2005 Mabry finished the season with a .265 average as a pinch-hitter.

He retired as an active player in 2007 with a respectable .263 batting average, nearly 1000 hits, and three trips to the post-season including the World Series. Mabry had a fulfilling fourteen-year career as a Major League player.

After he retired John served one year as a pre/post-game analyst for St. Louis Cardinals televised games. From 2012-2018 he rejoined the Cardinals as the batting coach, and in 2020 became a coach with the Kansas City Royals where he currently serves.

Mabry lives in St. Louis during the off-season with his wife Ann and their four children.