Following the 2018 season, Paul Rabil launched the Premier Lacrosse League, baiting over 140 MLL players to migrate over. However, the Cannons maintained more of their roster than other teams like the Dallas Rattlers or Rabil's New York Lizards. Two months prior to the start of the 2019 season, the league cut the team roster from nine to six when the Ohio Machine and Florida Launch folded and Charlotte Hounds suspended operations for two seasons. Taking this to their advantage, the Cannons posted a 9–7 record in 2019, good enough for the third of four postseason seeds and gave Boston its first playoff berth since 2015. Boston faced the Denver Outlaws in the semifinal, who were also hosting Championship Weekend. The Cannons got off to a hot start and led by as many as six goals, but ultimately fell, 17–15, ending their season.