Dumoulin was selected by the Carolina Hurricanes in the second round (51st overall) of the 2009 NHL entry draft, and previously played for the Pittsburgh Penguins and the Seattle Kraken.

Growing up in Maine, Dumoulin played hockey for the Biddeford High School Tigers where he helped them win back-to-back state championships.

In his second tournament at the international level, Dumoulin helped lead Team USA to a bronze medal at the 2011 World Junior Ice Hockey Championships.

[2] However, he was unable to qualify for the top tier Biddeford youth hockey team and as such, played pee wee and bantam in New Hampshire with the Seacoast Spartans.

[11] As a senior during the 2008–09 season, Dumoulin helped the team capture the regular-season championship and was named the EJHL’s Defensive Player of the Year.

[2] While playing with the Eagles, Dumoulin was surrounded with Pittsburgh Penguins prospects Carl Sneep, Philip Samuelsson, and Brian Gibbons.

He began the season strong, recording 10 points through 16 games, before being selected for Team USA at the 2011 World Junior Ice Hockey Championships.

[24] Prior to the tournament, Dumoulin was named a finalist for the 2012 Hobey Baker Award as he led all Hockey East defensemen in scoring.

[25] Following the Eagles' NCAA win, Dumoulin was again selected for the All-Tournament Team alongside teammates Johnny Gaudreau and Parker Milner.

[12] However, a few months later on June 22, 2012, Dumoulin was traded to the Pittsburgh Penguins, along with Brandon Sutter and the 8th overall selection (Derrick Pouliot) in the 2012 NHL entry draft, for center Jordan Staal.

[28] After attending the camp, Dumoulin was re-assigned to their American Hockey League (AHL) affiliate, the Wilkes-Barre/Scranton Penguins, to begin the 2012–13 season.

[31] He scored his first NHL point, an assist on Chris Conner's goal, in a game two days later against netminder Jonathan Bernier of the Toronto Maple Leafs.

[37] He competed with the Penguins during their first-round matchup against the New York Rangers, skating an average of 14:06 minutes a night through five postseason games.

[39] During the 2015 offseason, Dumoulin remained in Boston with two of his former Eagles teammates to continue off-ice workouts under strength and conditioning coach Russ DeRosa.

[41] Dumoulin was eventually paired with Trevor Daley and continued as one of Pittsburgh's most consistent defensemen with 16 assists and a plus-11 rating by March.

[42] Once the postseason began, Dumoulin scored his first NHL playoff goal in Game 5 of the Eastern Conference Final against the Tampa Bay Lightning.

[45] With a 3–1 win over the San Jose Sharks, Biddeford-born Dumoulin became the first Maine-born NHL player to hoist the Stanley Cup.

[46] Following the Stanley Cup win, Dumoulin returned to Boston and signed up for a summer course in order to finish his bachelor’s degree in marketing.

[1] His sole regular season goal came on April 4, 2017, after going 151 regular-season games without scoring, against the Columbus Blue Jackets in a 4–1 win.

[62] Dumoulin re-joined the Penguins for the 2018–19 pre-season but suffered an upper body injury during a game against the Columbus Blue Jackets.

[64] He remained a consistent member of the Penguins lineup before being diagnosed with a concussion following their 2019 NHL Stadium Series matchup against the Flyers.

At the start of the season, he missed two games due to a lower-body injury after being a late scratch for their 3-0 loss to the Vegas Golden Knights.

[72] He finished the shortened 2020–21 season logging an average of 22 minutes, 21 seconds per game, including a team-best 2:45 on the penalty kill.

[76] On July 1, 2023, Dumoulin left the Penguins as a free agent after 10 seasons and was promptly signed to a two-year, $6.3 million contract with the Seattle Kraken.

With a year remaining on his contract, Dumoulin was traded after just one season with the Kraken to the Anaheim Ducks in exchange for a fourth round pick in 2026 on July 2, 2024.

[81] In his second tournament at the international level, Dumoulin helped lead Team USA to a bronze medal at the 2011 World Junior Ice Hockey Championships.