Oakland Athletics
The Oakland Athletics selected Maxwell in the second round of the 2012 Major League Baseball draft. He made his debut that year with the AZL Athletics, and was promoted to the Vermont Lake Monsters of the Low-A New York-Pennsylvania League after six games. For Vermont, he batted .254 with 22 RBIs and was charged with 18 passed balls in 38 games. In 2013, playing for both the Beloit Snappers in the Single-A Midwest League and the Stockton Ports in the High-A California League, he batted .275 with seven home runs and 49 RBIs in 104 games between both teams.
In 2014, Maxwell batted .243/.334/.334 between Stockton and the Midland RockHounds of the Double-A Texas League. In 2015, he spent the whole season at Midland, batting .243/.321/.308 in 96 games.
Maxwell began 2016 with the Nashville Sounds of the Triple-A Pacific Coast League.
Maxwell was called up to the majors for the first time on July 23, 2016. He made his major league debut that night. In 60 games for Nashville prior to his promotion, he was batting .321 with ten home runs and 41 RBIs. He spent the remainder of the season with Oakland after his promotion and batted .283/.337/.402 in 33 games.
Maxwell began 2017 with Nashville and was recalled and optioned multiple times before he was called up to Oakland for the remainder of the season on June 22. In 76 games for Oakland, he batted .237 with three home runs and 22 RBIs.
On September 23, 2017, Maxwell became the first MLB player to join other US athletes protesting racial injustice by kneeling during the national anthem; Maxwell placed his hand over his heart, and teammate Mark Canha stood next to Maxwell and put a hand on his shoulder in support. Maxwell's actions came in response to President Donald Trump's comments that professional football franchise owners should fire players who knelt during the anthem. On Twitter and through his agent, Maxwell said his decision to kneel represented concern for racial injustice as well as freedom of speech and exercise of peaceful protest. The Oakland Athletics immediately issued a statement saying the team "pride[s] ourselves on being inclusive" and supports "players' constitutional rights and freedom of expression." While supported by the A's, Maxwell's future career in the MLB was seen as impacted by the reaction to his kneeling. He remained the only MLB player to protest by kneeling until 2020, when the league allowed for "Black Lives Matter" patches and organized league-wide kneeling for social justice in the aftermath of the nationwide protests of the murder of George Floyd by police in Minneapolis.
Subsequently, Maxwell said that while eating at a restaurant with a city councilman with whom he had attended high school, Devyn Keith, and another friend in Maxwell's hometown of Huntsville, Alabama, a waiter objected to Maxwell's protest and refused to serve their table. The waiter denied the story, saying he did not know who Maxwell was.
Maxwell began 2018 with Oakland. He was placed on the restricted list on May 16 when the Athletics entered Canada to play the Toronto Blue Jays, as he was not eligible for entry into Canada as he had not yet been sentenced for his assault with a deadly weapon charge that was placed in the previous off-season. He was designated for assignment on September 1, 2018. Maxwell cleared waivers and was sent outright to Triple-A Nashville on September 6. For the season with the A's, he batted .182/.207/.309 with one home run. He elected free agency following the season on November 2.