The actor is in talks for an undisclosed role in Venom, the Tom Hardy-led Spider-Man off-shoot from Sony.
Hardy is starring as the popular Marvel Comics antihero with Riz Ahmed, Michelle Williams and Jenny Slate also on the roll call.
If a deal makes, it would mark a reunion for Harrelson with director Ruben Fleischer, who directed the actor in the hit 2009 zombie comedy Zombieland. Venom is already deep into production - filming began in October - and rumors of Harrelson's involvement and swirled on-and-off.
Sony, who had no comment., will release Venom on...