Adam was born in Riverside, where he attended J.W North High School, playing baseball and basketball for the Huskies. For North baseball, he was an accomplished second baseman through 1994, which led to a scholarship to Cal State Northridge. Adam excelled at shortstop for the Matadors and set school records in career hits, RBI and batting average.
He led the nation in hits as a sophomore and junior and was a three-time All American. Kennedy was drafted in the first round (twentieth overall) by the St. Louis Cardinals in the 1997 Major League draft. In the minors with the Memphis Redbirds, he hit .327 with 10 home runs and 63 RBI in 1999. He was selected as a Pacific Coast League All-Star, Baseball America first-team Minor League All-Star and Triple-A All-Star. Adam made his major league debut that same year for the St. Louis Cardinals where he appeared in 33 games with a .255 batting average.
Southern California fans were overjoyed when Kennedy was traded the following year to the Anaheim Angels because they could easily get to see their hometown hero. That season, Adam matched a team record with eight RBI against the Blue Jays on April 18, 2000, the most RBI by any rookie in one game in 25 years. In a memorable seven season career with the Angels, Adam hit .280 in 992 games, with 51 home runs and 353 RBI.
He is most famous for holding a record (with five other players) for the most home runs in one postseason game, with 3 against the Twins in 2002, during the Angels Championship run. In total, Adam played in 1,691 career games in his stellar Major League career that spanned 13 years.