McInerney has scored 43 goals while playing for four teams in his Major League Soccer career.
He was drafted by Philadelphia in 2010 and scored 24 goals for the club before getting traded to Montreal in 2014. He also played for Columbus before joining Portland last season.
Welcome to Los Angeles, @JackMcInerney9! pic.twitter.com/aHUt4YoQ8D
- LA Galaxy (@LAGalaxy) April 18, 2017
McInerney scored five goals in 24 games last season for the Timbers, who placed him on waivers last monthwhen they needed space in the salary budget to sign a center-back.
The Galaxy are a disappointing eighth in the Western Conference after two wins and four losses to open the season. They host defending league champion Seattle on Sunday.