Kluwe, 32, in an article published Thursday on the website Deadspin, accused Vikings special-teams coach Mike Priefer of using homophobic language during the 2012 season and of wanting him off the team because of Kluwe's same-sex marriage activism.
Priefer has denied the accusation, and the Vikings said Friday Kluwe's claims would be investigated independently.
The Vikings had previously stated Kluwe's release was motivated by football-oriented reasons.
Kluwe, in a statement released Monday, said, "I want the truth to come out from the investigation, not in litigation," but he will be represented in the investigation by Minneapolis lawyer Clayton Halunen and the National Center for Lesbian Rights, the St. Paul Pioneer Press reported Tuesday.
"It's obvious to me...Chris paid a steep price for speaking out in favor of same-sex marriage rights in 2012 when he was a Vikings player. Ultimately it may have cost him both his job with the Vikings and his career as an NFL player," Halunen said in a statement.