The Boston Red Sox selected Reddick in the 17th round of the 2006 MLB draft, and he made his major league debut in 2009.

He also played in Major League Baseball (MLB) for the Oakland Athletics, Los Angeles Dodgers, Houston Astros and Arizona Diamondbacks.

He made his major league debut that night, pinch-hitting for Rocco Baldelli in the ninth inning and grounding out against Cla Meredith of the Baltimore Orioles in his only at-bat.

[3] Reddick was recalled the next day when Rocco Baldelli was placed on the disabled list with a left ankle contusion.

Reddick again started 2011 in Pawtucket but was recalled on May 26, 2011, after Darnell McDonald was placed on the 15-day disabled list with a strained left quad.

On December 28, 2011, the Red Sox traded Reddick and minor league players Raúl Alcántara and Miles Head to the Oakland Athletics for Andrew Bailey and Ryan Sweeney.

[5] Reddick finished 2012 with 32 home runs and 85 RBIs, both career highs, as he helped lead the A's to the American League West division title.

But on August 9, 2013, Reddick hit 3 home runs in a single game for the first time in his career in a 14–6 rout against the Toronto Blue Jays.

After the season, Reddick underwent arthroscopic surgery on his wrist, which caused him to miss 37 games on the disabled list.

[11] On August 1, 2016, the Athletics traded Reddick and Rich Hill to the Los Angeles Dodgers for Grant Holmes, Jharel Cotton, and Frankie Montas.

[16] In Game 2 of the ALCS, Reddick made a leaping catch to rob Chase Headley of a home run in the third inning against the Yankees.

The Astros went on to win the 2017 World Series, giving Reddick his first championship, amid a sign stealing scandal.

[17] In April 2018, Reddick became the second Astro in franchise history to hit two grand slams in one calendar month, Jeff Bagwell having been the first to do it (in May 2001).

[28] Despite Reddick's previous retirement announcement in May, he later signed for the Perth Heat in the Australian Baseball League in October 2022.