GWS players face potential AFL sanctions, with an investigation underway after an anonymous complaint about an end-of-season function.

The league and the Giants have confirmed they are looking into what happened at the event last month, days after their season ended with the semifinal loss to premiers Brisbane.

"The AFL and GWS have been undertaking an investigation into the Giants players' post-season event, which is in its final stages," the league said in a statement.

The AFL and the Giants have not confirmed what prompted the investigation, or what action the league might take.

GWS released a statement late on Tuesday, saying: "the Giants are aware of an anonymous allegation of inappropriate behaviour at the players' end-of-season function last month.

"The club and its integrity unit have been working with the AFL's integrity unit to investigate."

GWS had a straight-set exit last month after finishing fourth in the regular season, blowing leads in their qualifying final against Sydney and the home semifinal against the Lions.

AAP