Nicknamed "Big Rig", Maroon has previously played for the Anaheim Ducks, Edmonton Oilers, New Jersey Devils, St. Louis Blues, Tampa Bay Lightning, Minnesota Wild, and Boston Bruins.

Growing up in St. Louis, Maroon attended Oakville High School where he was recruited to play in the North American Hockey League (NAHL) by Kelly Chase and Al MacInnis.

[4] He played minor ice hockey for the St. Louis Amateur Blues from 2003 until 2005[5] where he was nicknamed "Fat Pat" due to his size, 6 ft 1 in (1.85 m) and 260 lb (120 kg).

[6] In order to improve on his playmaking ability, Maroon would stickhandle a golf ball in his garage for hours and skate in roller rinks.

[6] When he entered high school with his older brother Justin, Maroon earned a spot on the varsity team as a freshman.

[2] Prior to his selection, Maroon was ranked by the NHL Central Scouting Bureau as a "B" prospect, meaning he was expected to be drafted in the later rounds.

[13] Maroon had been invited to the Flyers' rookie and main training camps but was reassigned to the Knights after one exhibition game with their American Hockey League (AHL) affiliate.

For two months, he skated with the Montclair State University Red Hawks Men's Hockey team to stay in shape.

[2] On November 21, 2010, Philadelphia traded Maroon and David Laliberté to the Anaheim Ducks in exchange for forward Rob Bordson and defenseman Danny Syvret.

[23] The 2012–13 season was shortened due to a lockout but when the Ducks returned to play, Maroon was placed on a line with Mathieu Perreault and Teemu Selanne.

[29] Maroon was one of the Ducks' most consistent players during their series, finishing third on the team in goals and power play points as well as limited his penalty minutes.

[2] On February 29, 2016, Maroon was traded to the Edmonton Oilers in exchange for Martin Gernát and a fourth-round pick in the 2016 NHL entry draft.

[31] He made his Oilers debut on March 3 against the Philadelphia Flyers, where he scored his fifth goal of the season during the second period to bring their lead to three.

[32] After scoring against his old organization, Maroon said "it all hit me...it brought me back to my time in Philly, when I didn't know how to train, I was out of shape, my dark days.

The Oilers Head Strength and Conditioning Coach Chad Drummond teamed him up with a nutritionist who helped him manage his portion controls and eating habits.

[34] On April 11, 2016, Maroon was named to Team USA's 2016 IIHF World Championship roster alongside teammate Matt Hendricks.

[36] In his debut game with the United States men's national ice hockey team, Maroon scored their first and only goal in an eventual 5–1 loss to Canada.

In the Oilers first home game on October 12, Maroon scored the first goal in the Rogers Place arena in a 7–4 victory over the Calgary Flames.

[41] Maroon continued to play the remainder of the 2016–17 season with the Oilers alongside Connor McDavid where they recorded a combined Corsi percentage above 50 percent.

[45] In March, Maroon was named the Oilers nominee for the Bill Masterton Memorial Trophy, given to a player who "best exemplifies the qualities of perseverance, sportsmanship, and dedication to ice hockey.

[47] Upon winning their first series against the Sharks, Maroon and the Oilers began the Western Conference Second Round against the Anaheim Ducks.

"[52] On February 25, 2018, Maroon was traded to the New Jersey Devils in exchange for J. D. Dudek and a third-round pick in the 2019 NHL entry draft.

[38] The Blues qualified for the 2019 Stanley Cup playoffs as the third seed from the Central Division, capping a turnaround in a campaign that saw them in last place in the NHL as late as January 2019.

Playing the [[Toronto Maple Leafs in the first round of the playoffs for a second consecutive year, Maroon and the Lightning would go on to lose the series in six games.

On July 2, 2023, Maroon's four-year tenure with the Tampa Bay Lightning concluded when he was traded due to salary cap considerations, along with Maxim Cajkovic, to the Minnesota Wild in exchange for a seventh-round pick in 2024.

[76] Still recovering from his back surgery, the Bruins placed Maroon on long term injured reserve (LTIR) just after being acquired.

[78] Maroon would score his first point as a Bruin in Game 1 of the opening round against the Toronto Maple Leafs, an assist on a goal by John Beecher.

As a free agent from the Bruins, Maroon moved to his eighth NHL outfit after securing a one-year, $1.3 million contract with the Chicago Blackhawks on July 1, 2024.

[79] Maroon is married to Francesca Vangel, another St. Louis native[80] whose family runs a restaurant called Charlie Gitto's.

[2] In November 2022, after Bruins commentator Jack Edwards remarked about his weight during a game broadcast, Maroon donated $2,000 to a Tampa Bay charity to support those struggling with mental health and body image.