Benn was drafted by the Dallas Stars 129th overall in the 2007 NHL Entry Draft from the Victoria Grizzlies. Following his draft, Benn began his major junior career with the Kelowna Rockets in the WHL. He scored 65 points in his rookie season in 2007–08, then improved to a team-high 46 goals to go with 36 assists and 82 points in just 56 games in 2008–09. After being named to the WHL West First All-Star Team, Benn paced the Rockets with a playoff-leading 33 points en route to the 2009 Ed Chynoweth Cup title. In the subsequent 2009 Memorial Cup tournament, held in Rimouski, Quebec, Benn notched a four-goal game and added an assist in the second round-robin match against the Drummondville Voltigeurs, a 6–4 win, to secure the Rockets a berth in the tournament final. Although Benn's Rockets lost to the Windsor Spitfires 4–1 in the Final, Benn was named to the Tournament All-Star Team, along with teammate Tyler Myers.
Professional
Dallas Stars
Benn made the Stars' roster for the 2009–10 season and scored his first NHL goal on October 11, 2009, against Roberto Luongo of the Vancouver Canucks. Benn tied the score 3–3 late in the game, but the Stars lost later in the shootout. At the end of his rookie season, he was sent down to the Stars' AHL affiliate Texas Stars in the suburbs of Austin for the 2010 Calder Cup playoffs. He scored 14 goals and had 26 points in 24 playoffs games as Texas fell to the Hershey Bears in the Calder Cup Finals. Benn later spoke of the experience, "I had a fun summer here...it was a big part of my hockey career and helped me develop my game. I definitely loved playing here." Benn took an opportunity in February 2011 after teammate Brad Richards' concussion to take a leading role with the team. During the All Star Game's SuperSkills Competition, Benn participated in the Accuracy Shooting contest and won his leg against Steven Stamkos and Jonathan Drouin then the finals against Philadelphia Flyers rookie Matt Read with times of 13.583 and 10.204 seconds respectively. With the 2012–13 season delayed due to the labour lock-out, Benn signed a contract for the duration of the dispute with the Hamburg Freezers of the GermanDEL on October 2, 2012. Unable to initially agree to a contract with the Stars, Benn missed the first four games of the shortened NHL season before re-signing to a five-year, $26.25 million contract on January 24, 2013. during the 2013 off-season. Benn was named the sixth captain of the Dallas Stars on September 19, 2013. On April 11, 2015, Benn scored 4 points in the Stars' last regular season game to finish with 87 points on the season and win the Art Ross Trophy. His final point, a secondary assist with 8.5 seconds left in the game, allowed him to overtake John Tavares for the award. On July 15, 2016, Benn agreed to an eight-year, $76 million contract extension with Dallas that runs through the 2024–25 NHL season at an average annual value of $9.5 million.
International play
Playing in his second WHL season, Benn was named to Team Canada, along with Kelowna Rockets teammate Tyler Myers, for the 2009 World Junior Championships in Ottawa. He contributed 4 goals and 2 assists in 6 games, helping Canada to its record-tying fifth straight gold medal, defeating Sweden 5–1 in the final. Benn first represented the senior team at the 2012 IIHF World Championship. On January 7, 2014, Benn was named to the Canadian Olympic hockey team for the 2014 Winter Olympics in Sochi despite not being invited to the orientation camp during the summer of 2013. In his first game as an Olympian, Benn scored the game-winning goal in Canada's first game against Norway in a 3–1 victory. He scored the only goal in a 1–0 win against the United States in the semi-final, to advance Canada to the gold medal game, where they eventually beat Sweden 3–0.
