He was a highly touted prospect heading into the 2008 NHL entry draft, where he was selected in the first round, fifth overall, by the Toronto Maple Leafs.

[1] When he played in Toronto his charity "Luke's Troops" helped military families attend Maple Leafs home games.

[3] While playing with the Contacts, Schenn was selected in the first round, 20th overall, of the 2004 Western Hockey League (WHL) bantam draft by the Kelowna Rockets.

[3] Later in that same season, Schenn was named to the WHL's roster for the ADT Canada-Russia Challenge[3][6] and participated in the annual Canadian Hockey League Top Prospects Game, where he served as a team captain and scored a goal.

[7] While playing in Kelowna, he was often paired with current Vancouver Canucks defenceman Tyler Myers, former winner of the NHL's Calder Memorial Trophy.

[9] Early reports from the Maple Leafs training camp in September 2008 indicated Schenn was likely to be returned to his junior club for the 2008–09 season.

[7][10] After training camp, Schenn was chosen for the team roster at the start of the 2008–09 season,[11] making his NHL debut on October 9 against the Detroit Red Wings.

[20] When Kaberle was traded to the Boston Bruins in February 2011, Schenn was briefly named an alternate captain in his place,[21] until Colby Armstrong returned to the line-up after an injury.

[22] Wilson felt that Schenn had made significant strides in his third NHL season: "He's learned a lot...He's not on the ice for as many goals against any more.

"[23] At the end of the season, Schenn had tied his career-high for goals with five and set new personal records for assists (17) and total points (22) while playing in all 82 games for the Maple Leafs.

[26] During the 2015–16 season, Schenn appeared in 29 games for 5 points before he was traded (alongside Vincent Lecavalier) to the Los Angeles Kings in exchange for a third-round pick in 2016 and prospect Jordan Weal on January 6, 2016.

[30] Assigned to American Hockey League (AHL) for the first time in his career, Schenn joined the Ducks' affiliate, the San Diego Gulls, and contributed with 10 points in 22 games before he was traded (along with a seventh-round pick in 2020) to the Vancouver Canucks in exchange for Michael Del Zotto on January 16, 2019.

[33] Following a second successive Stanley Cup with the Lightning in the 2020–21 season, Schenn left Tampa Bay as a free agent and was signed to a two-year, $1.7 million contract to return to previous club, the Vancouver Canucks on July 28, 2021.

[34] During the 2022–23 season, Schenn surpassed Brooks Orpik to become the all-time leader in hits by an NHL defenceman after executing six against the Arizona Coyotes on December 3, 2022.

[35] As a free agent from the Maple Leafs in the off-season, Schenn was signed to a three-year, $8.25 million contract with the Nashville Predators on July 1, 2023.

[3][6] During the 2007–08 season, Schenn was named to Canada's selection camp roster for the 2008 World Junior Ice Hockey Championships.

[38] The final roster was named December 13, 2007, and Schenn was selected for the team, being paired with Thomas Hickey as the top defensive tandem.

[42] Schenn, along with then-Toronto teammates Dion Phaneuf and James Reimer, played for Canada at the 2011 IIHF World Championship.

[6] His younger brother Brayden was picked fifth overall in the 2009 NHL entry draft by the Los Angeles Kings,[48] and was later traded to the Philadelphia Flyers.

During his rookie season, he donated $10,000[49] to start Luke's Troops, a charity which allows Canadian servicemen and women to attend the team's home games as Schenn's guest.