He played in MLB for 19 seasons with the Atlanta Braves, Los Angeles Dodgers, San Francisco Giants, and Oakland Athletics.

After retiring as a player, Baker served as the manager of the Giants from 1993 to 2002, the Chicago Cubs from 2003 to 2006, the Cincinnati Reds from 2008 to 2013, the Washington Nationals from 2016 to 2017, and the Houston Astros from 2020 to 2023.

When the younger Baker wanted to quit baseball and have a paper route, his father told him that he did not raise a son who was a quitter as a way to try to encourage him to spin his attitude in a positive direction.

His tenure began in 1976 with a meager .242 batting average in 112 games that saw him collect just 93 hits with 39 RBIs while suffering a problem with his stretched knee ligaments that required surgery after the season ended.

Baker proved key in Game 2 when he hit a grand slam in the fourth inning to break a 1–1 tie that the Dodgers won 7–1.

[23] In the 1978 World Series, they met the Yankees again, with the same result for Baker and the Dodgers (complete with him hitting only one home run) as he batted .238 in the six-game loss.

In his final season of 1986, he began wearing a wristband (featuring his face), which he has continued to do as a manager; he has stated it is to help wipe perspiration off his forehead.

[34][35][36] Baker was working as a stockbroker in 1987 when he received a call from Hank Aaron, Joe Morgan, and Frank Robinson to go to Dallas, Texas to try to get jobs for minority baseball players after they finished their playing careers, which came in the wake of controversial remarks by Dodgers general manager Al Campanis on April 6, 1987.

On the advice of his father, Baker, alongside his brother and daughter, set out to Lake Arrowhead to pray and seek guidance to decide whether he should see Rosen and possibly return to baseball.

The Giants lost 12–1 on the final day of the season when a win could have forced a tiebreaking game with Atlanta for the division championship (the following year, a Wild Card was instituted in both leagues).

Since the Giants missed the playoffs (as only the division winners qualified before 1995), he also became the eighth and so far the last manager to lead a team to 100 wins without making it to the postseason.

The Giants faced the St. Louis Cardinals (who had beaten the Arizona Diamondbacks, the defending champions) in the 2002 National League Championship Series.

[46] Despite Baker's success in San Francisco, he had an increasingly strained relationship with owner Peter Magowan, one that even the Giants' first pennant in 13 years could not mend.

The Giants did not renew his contract after the season,[47] letting him leave to manage the Chicago Cubs and hiring Felipe Alou to replace him.

On November 15, 2002, he was hired by the Chicago Cubs to a four-year deal to manage the team, replacing Bruce Kimm, who had taken over when Don Baylor was fired in the middle of the third 90-loss season in four years.

"[51] With the help of an impressive pitching staff and big gun batters such as Sammy Sosa and Moisés Alou, the Cubs claimed their first division title in fourteen years.

In Game 6, with Chicago, five outs away from the pennant and holding a 3–0 lead, the infamous Steve Bartman foul ball incident near the fans in left field would unravel the Cubs and derail the chance for their first World Series appearance in 58 years.

The Bartman incident proved to be a distraction for fans and the media, but it was critical execution failures by the Cubs such as a wild pitch on a ball four, a fielding error on a potential inning-ending double play, and a bad throw from the outfield after a Marlins hit, which allowed the Marlins to score eight runs in that eighth inning to win the game 8–3; Cubs player Doug Glanville also stated that the loss in Game 5 (where Josh Beckett threw a two-hit shutout) was the true turning point of the series.

Reds general manager Walt Jocketty admitted the team's latest collapse played a role in the decision to fire Baker.

[71] In the two year gap between jobs, Baker called multiple franchises looking to fill their respective vacancies, such as the Detroit Tigers, the Seattle Mariners, and the San Diego Padres, but only the latter even gave him a callback (they later hired Andy Green).

[72] On November 3, 2015, Baker was named the new manager for the Washington Nationals for the 2016 season, his first managerial position since being fired by Cincinnati in 2013; he was hired to replace Matt Williams after a deal with Bud Black fell through.

[73] Comments made shortly after his hire raised attention when he suggested his Washington Nationals should field more players of color as "you've got a better chance of getting some speed with Latin and African-Americans.

On April 30, he passed Casey Stengel for 12th all-time with a 9–2 win over the Tampa Bay Rays, the teams' first meeting since the previous year's ALCS.

The White Sox were led by Tony La Russa, whom Baker had faced as manager over 200 times previously, and whose careers both had intertwined and spanned more than five decades.

On November 5, 2021, Astros owner Jim Crane announced that Baker had agreed to a one-year extension to manage the club for the 2022 season.

Baker was named manager of the American League in the MLB All-Star Game played at Dodger Stadium in Los Angeles.

[107] Baker was named manager of the American League team for the 2023 MLB All-Star Game, played at T-Mobile Park in Seattle.

On the same day that Baker won his 2,000th game, his son Darren scored the winning run home for his High A team in Delaware on a sacrifice fly.

Baker had had surgery in December of that year to remove his prostate (his fears over potentially having the cancer return led him to name his three-year-old son as a batboy to "show him the world").

[128] For some time, Baker had troubles with the Internal Revenue Service, who had determined that his investments in tax shelters for some years (as guided by his brother Victor) were to be disallowed, which would have resulted in penalties of at least a million dollars with interest.