The 23-year-old forward, a restricted free agent, avoided a salary arbitration hearing scheduled for Aug. 3.
RELATED: [NHL Free Agent Tracker | NHL players file for salary arbitration]
He had 34 points (11 goals, 23 assists) in 77 regular-season games last season and eight points (two goals, six assists) in 24 Stanley Cup Playoff games.
Selected by Boston in the fourth round (No. 116) of the 2014 NHL Draft. Heinen has 81 points (27 goals, 54 assists) in 162 regular-season games and nine points (three goals, six assists) in 33 playoff games.