Gabe Kapler attended Moorpark College in the fall of 1994. There he was named First Team All-Western State Conference after batting .337. He was drafted by the Detroit Tigers in the 1995 Major League Baseball draft.

In 1998, with the Jacksonville Suns, Kapler won the Class AA Southern League "Most Valuable Player" Award. He was honored as Minor League "Player of the Year" by Baseball Weekly, The Sporting News, and USA Today, and was named Detroit's No. 1 prospect by Baseball America.

In November 1999, he was traded by the Tigers to the Texas Rangers. He hit two homers on Opening Day in 2000, and after a team-record 28-game hitting streak in July, he was named the American League's "Player of the Week".

In July 2002, the Rangers traded him to the Colorado Rockies, and was later acquired by the Red Sox in 2003, where he primarily played right field and batted .291. In 2004, he led the team with six outfield assists and hit .272

Less than one month after the Red Sox 2004 World Series victory, Kapler departed to play for Japan's Yomiuri Giants. But he struggled in Japan, and was placed on the inactive list in mid-season. He then came back to Boston and re-signed with the Sox.

In September however, he ruptured his left Achilles tendon while rounding the bases after a home run and had season-ending surgery. In June 2006, Kapler came back and hit .254 and played error-less outfield for the second year in a row. He announced his retirement from professional baseball in December but came back to play with the Brewers in 2008.

In 2023, Gabe Kapler was one of those interviewed by the Sox to be Head of Baseball Operations.