According to the Associated Press (via Boston.com), the lawsuit claims the league hid the true dangers of football.
Hernandez took his own life in prison while serving a life sentence for murder, but an autopsy revealed that he had been suffering from CTE.
Doctors reported Hernandez was in stage three out of four of the degenerative brain disease.
"We're told it was the most severe case they had ever seen for someone of Aaron's age," his lawyer Jose Baez said, per the AP's Jimmy Golen.
There was an original lawsuit placed in federal court against both the league and the New England Patriots, but the case was dropped Sunday, per Ken Belson of the New York Times.
The new lawsuit was placed in the state of Massachusetts, without the Patriots but with the addition of Riddell. Ben Volin of the Boston Globe reported that the team is expected to be added in a separate lawsuit at a later date.
The lawsuit is seeking damages to benefit Hernandez's daughter.