He has previously played in MLB for the Los Angeles Dodgers and Minnesota Twins and in Nippon Professional Baseball (NPB) for the Hiroshima Toyo Carp.

[1] In his rookie season of 2008, Maeda posted a 9–2 win–loss record with a 3.20 earned run average (ERA) in 19 games (18 starts).

[4] The Carp chose to make him available to Major League Baseball (MLB) teams through the posting system in December 2015.

[5] The deal was structured in this manner because Maeda's original physical with the team revealed some unspecified "irregularities.

[7] Maeda picked up the win in his MLB debut on April 6, 2016, pitching six shutout innings against the San Diego Padres at Petco Park.

[14] On June 18 he was back in the rotation and allowed only one run on three hits in five innings[14] but he returned to the bullpen after that game because the Dodgers had too many starting pitchers on the roster.

[15] However, he only appeared in one game in relief before returning to the starting rotation and from June 18 through August 25, he had gone 8–2 with a 2.70 ERA as a starter.

[16] At the end of the season, the Dodgers moved Maeda back into the bullpen in order to try him in that role for possible use in the playoffs.

[28] On September 1, 2021, it was announced that Maeda had undergone Tommy John surgery and will miss the entire 2022 season.

[30] Maeda struggled to a 7.26 ERA across his first 16 starts, and the Tigers announced he would be moving to the bullpen for the "foreseeable future" on July 11, 2024.

In the 2013 World Baseball Classic, he said he would use the tournament to assess his desire to compete in MLB, based on how he fared against their hitters.

[32] Maeda started two games in the pool rounds, against China and Netherlands, amassing a 2–0 record with 0.00 ERA, 0.30 WHIP, allowing just two hits, one walk striking out 15 in 10 innings.

[39] He throws from a three-quarters arm slot and his Japanese-style windup features a slight pause at the top of his leg kick.

[45] A fan of the reality television show Terrace House since its beginning, Maeda personally asked to be a guest commentator and appeared in episode 45 of the Opening New Doors season.