Heading into the 2011 NHL Entry Draft, Bärtschi was ranked by the NHL Central Scouting Bureau as the seventh best North American based skater, and was selected 13th overall by the Calgary Flames. The team quickly signed him to a three-year entry level contract US$1.45 million per season, including bonuses. He attended the team's training camp that fall, but was returned to Portland for the 2011–12 WHL season. Bärtschi was among the league's leaders offensively, averaging 2.00 points per game (94 points in 47 games) and was named WHL player of the week three times. His teammates named him Portland's most valuable player, and he was named to the WHL's Western Conference second all-star team.