Johansson, 28, has battled injuries in recent seasons. He was traded by the New Jersey Devils to the Bruins at the trade deadline in February and played only 10 regular-season games in Boston after suffering a lung contusion on a hit by the Carolina Hurricanes' Micheal Ferland.
After posting only a goal and two assists in those 10 games, Johansson bounced back with four goals and seven assists in 22 playoff games, forming a dynamic duo with Charlie Coyle on Boston's third line.
Johansson is coming off a three-year, $13.75 million contract that he signed with the Washington Capitals. His best season with the Capitals was 2016-17, when he had 24 goals and 34 assists in 82 games.
After a trade to the Devils, he played in only 29 games the next season and 58 last season, when he finished with 13 goals and 17 assists.