Adam LaRoche was a 1998 graduate of Fort Scott High School in Fort Scott, Kansas, where he played baseball. He was named an All-American in baseball as a senior. His uncle, Dave Regan, was his high school head coach. He played for his father, Dave, at Fort Scott Community College in 1999 before transferring to Seminole Community College in Seminole, Oklahoma in 2000, where he was an All-American and the MVP of the Junior College World Series.

He was drafted by the Florida Marlins in both the 1998 and 1999 amateur drafts, but refused to sign. He was drafted by the Atlanta Braves in 2000 and signed with the team.

LaRoche again platooned with Franco in 2005. While he did hit 22 home runs, LaRoche had a very streaky season. He hit .385 in his final 17 games of the year, but just .105 in the 19 games that preceded that streak. He batted .500 with a grand slam in the Braves 2005 NLDS Series against the Houston Astros. With the offseason departure of Franco, LaRoche became the Braves sole starter at first base in 2006.

On May 14, 2006, LaRoche garnered the contempt of Braves fans, players, and management after a play in which he fielded a routine grounder and lackadaisically jogged to first, and was beaten to the bag by Nick Johnson. LaRoche was heavily booed by the crowd (which continued for some time in the following games) and was benched for the play.

On May 28, 2006, LaRoche contributed two of the Braves’ record eight home runs in a remarkable win against the Chicago Cubs. In addition, in a wild game against the San Diego Padres on July 14, 2006, LaRoche hit two more home runs and had five RBIs to help the Braves to a 15–12, 11-inning win. He finished the year with a .285 average, 32 home runs, and 90 RBIs — all career-bests.

LaRoche suffers from ADHD that was diagnosed during his high school years, which occasionally leads to on field blunders such as in a game against the Washington Nationals in 2006, when he picked up a Nick Johnson ground ball that should have resulted in the third out of the inning, but did not move quickly to step on first base. Johnson beat LaRoche to the base; the inning continued, and the Nationals scored four unearned runs. Washington won 8-1, and LaRoche was benched for the next game.

The Braves traded LaRoche and minor league outfielder Jamie Romak to the Pittsburgh Pirates on January 17, 2007 for reliever Mike Gonzalez and minor league shortstop Brent Lillibridge.

During the 2009 season he played with his brother Andy LaRoche with the Pirates until July 22, 2009 when he was traded to the Boston Red Sox.

On May 13, 2009, LaRoche became the first player in major league history to have a home run taken away through the use of video replay.

On July 31, 2009, after only spending six games with Boston he was dealt back to his former Atlanta Braves for first baseman Casey Kotchman. LaRoche was traded by Boston in order to cut payroll and the belief that Kotchman would be a better pinch hitter than LaRoche would.

On January 14, 2010, LaRoche agreed to a 1-year, $4.5 million contract with the Arizona Diamondbacks. His deal included a $7.5 million mutual option with a $1.5 million buyout. In his 1-year tenure with the Diamondbacks, LaRoche hit .261 with 25 home runs and 100 RBI in 151 games.

On January 4, 2011, LaRoche agreed to a 2-year contract with the Washington Nationals. His contract paid him $7 million in 2011 and $8 million in 2012 with a mutual option for $10 million in 2013. On April 7, LaRoche hit his first home run as a member of the Nationals, a game-winning two-run home run off Florida Marlins reliever Edward Mujica in the 11th inning of a 5–3 Nationals win. His 2011 season ended with labrum surgery on his left shoulder with career-low batting numbers of .172/.288/.258 (BA/OBP/SLG).

LaRoche’s 2012 season began much more successfully, hitting .329 in April. He was a consistent bat throughout the season, driving in no fewer than 12 runs each month from April to August.

On January 8, 2013, LaRoche signed a 2-year, $24 million contract to remain with the Nationals, that included a mutual option for 2015. LaRoche had a down year in 2013, hitting .237 with 20 home runs and 62 RBI in 152 games.

LaRoche had a bounce back season in 2014, hitting .259 with 26 home runs and 92 RBI in 140 games. After the Nats were eliminated in the NLDS by the San Francisco Giants, the Nats announced they would not pick up LaRoche’s $15.3MM option, with the intent of moving Ryan Zimmerman to first base.

On November 25, 2014, the Chicago White Sox announced that LaRoche had been signed to a two–year, $25 million contract. LaRoche hit his 250th career home run off Detroit Tigers reliever Joakim Soria in a 4-3 White Sox win on June 6, 2015.

On March 15, 2016, LaRoche said that he intended to “step away from baseball.” He said that he would honor a request from teammates to reconsider his retirement for a day or two before making an official announcement. On the next day, it was revealed that LaRoche’s reason for a possible retirement was that the White Sox had placed a restriction on his 14-year-old son entering the team’s clubhouse every day. By retiring, LaRoche walked away from a $13 million contract. The following day, teammates were close to boycotting their spring training game until manager Robin Ventura stepped in and told the players to play. White Sox executive vice president Kenny Williams defended his request by stating “name one job in the country where you can bring your child to work every day.”