The NFLPA filed the grievance at the end of last week, and it will go to an independent arbitrator.
The suspension could prevent Gordon from getting an accrued season and delay him from reaching free agency. Gordon's suspension meant he was active for only five games; an NFL player needs six games active to have it count as an accrued season toward free agency.
The NFLPA plans to argue, among other things, that Gordon's missing a special-teams meeting did not constitute grounds for a one-game suspension.
Gordon intends to resume playing in the NFL after his one-year suspension ends after the 2015 season. He also was suspended for the 2014 season in August after a failed drug test, but the NFL later reduced his suspension to 10 games.
NFLPA Hoping to Get Josh Gordon To Free Agency Sooner
ESPN Browns reporter Pat McManamon discusses why the NFLPA has filed a grievance against the Browns for Josh Gordon's suspension at the end of the 2014 season.