Schenn began his professional career in the NHL during the 2008–09 season and played with the Maple Leafs until being traded to Philadelphia following the 2011–12 season. After his rookie season, Schenn's play was recognized when he was named to the NHL's All-Rookie Team. He has represented Canada internationally, winning a gold medal at the 2008 World Junior Ice Hockey Championships and a silver medal at the 2009 World Ice Hockey Championships with the nation's junior team.
Schenn is a stay-at-home defenceman whose main focus is preventing goals rather than scoring. With a physical style of play, he is usually among NHL leaders in hits. His charity "Luke's Troops" helps military families attend Maple Leafs home games. His younger brother Brayden was drafted by the Los Angeles Kings at the 2009 NHL Entry Draft but was traded and currently plays for St. Louis.
Schenn's first minor hockey team was the Saskatoon Red Wings, where he was coached by his father, Jeff. In 2004–05, Schenn played AAA midget hockey for the Saskatoon Contacts, who won the Telus Cup as Canada's national midget hockey champions. 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.
The Kelowna Rockets arranged for Schenn to join the team during their Memorial Cup run at the end of the 2004–05 season. He roomed with defenceman Shea Weber as the team wanted him to learn about his future role. Schenn debuted with the Rockets during the 2005–06 season, and was named the team's Rookie of the Year. He served as an alternate captain for the team during the 2007–08 season. Later in that same season, Schenn was named to the WHL's roster for the ADT Canada-Russia Challenge and participated in the annual Canadian Hockey League Top Prospects Game, where he served as a team captain and scored a goal. While playing in Kelowna, he was often paired with current Winnipeg Jets defenceman Tyler Myers, former winner of the NHL's Calder Memorial Trophy. Schenn was named to the WHL's Second All-Star Team after the 2007–08 season.
Leading up to the 2008 NHL Entry Draft, Schenn was a highly-regarded prospect, ranked fifth among draft-eligible North American skaters by the NHL Central Scouting Bureau. Some scouts saw him as a mix between Calder Trophy and Norris Trophy nominee Dion Phaneuf and two-time Stanley Cup champion Adam Foote. E. J. McGuire, then-director of the Central Scouting Bureau, compared him to former first overall selection Ed Jovanovski. At the Draft, the Toronto Maple Leafs traded with the New York Islanders for a higher draft pick, which they ultimately used to select Schenn.
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. On October 7, 2008, he signed a contract with the Maple Leafs with a base salary of $850,000 per season and performance bonuses that could raise the value as high as $1.25 million per season. After training camp, Schenn was chosen for the team roster at the start of the 2008–09 season, making his NHL debut on October 9 against the Detroit Red Wings. On October 29, Schenn recorded an assist for his first career NHL point against the New Jersey Devils. Later in the season, he scored his first goal against Montreal Canadiens goaltender Carey Price. In January 2009, Schenn missed 12 games with a lower-body injury, the only games he missed during his rookie season. Schenn played for the Rookie YoungStars team in the 2008–09 NHL YoungStars Game. On March 14, 2009, he recorded his first multi-point (two assists) game in an 8–6 win against the Calgary Flames. The NHL named Schenn to the 2008–09 All-Rookie Team on June 18, 2009, along with fellow 2008 draftee Drew Doughty. The award acknowledged Schenn's defensive prowess and physical play, as he led all NHL rookies in blocked shots and all rookie defencemen in hits. Schenn finished his first season in the NHL with two goals and 12 assists in 70 games played.
Expectations for Schenn were high heading into the 2009–10 season. During training camp, Toronto Head Coach Ron Wilson named him as one of the team's top four defencemen. As the season progressed, however, Schenn's play was disappointing, and Wilson kept him out of the line-up for a game in October and again for a three-game stretch in December. Towards the end of the season, Schenn and some of his younger teammates improved their play. In a game against the Ottawa Senators, Schenn posted his first career two-goal game, helping him finish the season with new career-highs in goals (5) and points (17) in 79 games played.
Schenn had a strong start to the 2010–11 season, playing with veteran Tomáš Kaberle. Prior to a game against the Philadelphia Flyers, Wilson assessed Schenn's play as "great." When Kaberle was traded to the Boston Bruins in February 2011, Schenn was briefly named an alternate captain in his place, until Colby Armstrong returned to the line-up after an injury. 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." 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.
On June 23, 2012, Schenn was traded to the Philadelphia Flyers in exchange for James van Riemsdyk. With the Flyers, Schenn was given the opportunity to play alongside his younger brother Brayden, saying, "It’s going to be exciting to play with my brother, that’s for sure. I can’t describe how cool this is." On June 28, 2012, it was announced that Schenn was going to wear number 22 for the Flyers, as his usual number 2 was retired from the team in honour of defenceman Mark Howe.
During the 2015–16 season, Schenn appeared in 29 games for 5 points before he was traded by the Flyers alongside Vincent Lecavalier to the team that drafted his brother Brayden 5th overall in the 2009 NHL Entry Draft, the Los Angeles Kings, in exchange for a third round pick in 2016 and prospect Jordan Weal on January 6, 2016.
On July 23, 2016, he signed a two-year, $2.5M deal with the Arizona Coyotes.
Schenn's first experience with Hockey Canada was as a member of Team West at the 2006 World Under-17 Hockey Challenge in Regina, Saskatchewan, where his team finished seventh. He played for Canada twice at the under-18 level: the 2006 Ivan Hlinka Memorial Tournament, where his team won gold, and the 2007 IIHF World U18 Championships, where Canada finished fourth. Schenn scored three goals during this tournament.
In 2007, Hockey Canada assembled a junior team to represent Canada in an eight-game series (the 2007 Super Series) against a Russian junior team to commemorate the 35th anniversary of the 1972 Summit Series. Canada went undefeated in the eight games, with seven wins and one tie, while Schenn recorded 24 penalty minutes and no points.
During the 2007–08 season, Schenn was named to Canada's selection camp roster for the 2008 World Junior Ice Hockey Championships. 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. Canada won the gold medal and Schenn finished the tournament with a plus-minus rating of +5 to lead the team. Hockey analyst Pierre McGuire dubbed him "the human eraser" for his play internationally.
After his rookie season in the NHL, Schenn was named to the senior Canadian roster for the 2009 IIHF World Championship. He played all nine games for Canada, but did not significant ice time, averaging just under seven minutes per game. In the tournament he recorded just one assist. Canada took home the silver medal after a 2–1 loss to Russia in the gold medal game. Schenn, along with then-Toronto teammates Dion Phaneuf and James Reimer, played for Canada at the 2011 IIHF World Championship. Canada placed fifth in the tournament, with their only loss coming in the quarter-finals against Russia. In seven games, Schenn recorded a single assist.
After the 2012–13 season, Schenn was again selected by Hockey Canada to participate in the 2013 IIHF World Championship alongside Flyers teammates Matt Read, Wayne Simmonds and Flyers captain Claude Giroux. Canada was eliminated by Sweden in the quarter-finals, leaving them without a medal for the second-straight year.
Schenn is a defensive-defenceman who plays a physical game while attempting to prevent opponents from scoring. Since his rookie season, he has been among the NHL leaders in hits. He believes he is at his best when he is playing a tough game, while staying responsible: "You just want to be physical and play with a bit of an edge, but you don't want to put your team down short-handed." Growing up, Schenn patterned his play after fellow defencemen Chris Pronger and Rob Blake.
Schenn was born on November 2, 1989, in Saskatoon, Saskatchewan. His parents are Jeff and Rita Schenn. His younger brother Brayden was picked fifth overall in the 2009 NHL Entry Draft by the Los Angeles Kings, and was later traded to the Philadelphia Flyers. Schenn also has two younger sisters, Madison and Macy. Luke Schenn graduated from St. Joseph High School in Saskatoon. His brother Brayden, along with fellow NHLers Colby Armstrong, Riley Armstrong and Jarret Stoll, also attended St. Joseph when they lived in Saskatoon.
Schenn married his longtime girlfriend Jessica Peczek on July 18, 2015 in Kelowna.
Schenn was a key contributor to the Maple Leafs' efforts to honour Canada's military. During his rookie season, he donated $10,000 to start Luke's Troops, a charity which allows Canadian servicemen and women to attend the team's home games as Schenn's guest. Fans at the games often recognized the soldiers with applause. "They have served overseas so it's good that the fans show their appreciation," Schenn said. In February 2011, Schenn's contributions to the military were acknowledged when he was recognized during the team's annual Armed Forces night.