The wrongful death lawsuit, filed in San Diego Superior Court by Seau's children and ex-wife, as well as the trustee of his estate, also claims that the NFL concealed the risks of brain damage in the sport, court documents showed.
"We know this lawsuit will not bring back Junior," the Seau family said in a written statement. "But it will send a message that the NFL needs to care for its former players, acknowledge its decades of deception on the issue of head injuries and player safety, and make the game safer for future generations."
An NFL spokesman, Greg Aiello, told Reuters the league's attorneys would review the lawsuit and respond to the claims appropriately through the court.
Seau, a 12-time Pro Bowl linebacker for the Chargers and two other teams, died in May 2012 after shooting himself in the chest at his beachfront house in his hometown of Oceanside, California.
A study by a team of independent researchers released earlier this month found that Seau, 43, suffered from chronic traumatic encephalopathy, or CTE - the same debilitating brain disease diagnosed in at least two other former NFL players who committed suicide.
The NFL has previously said the result of the examination of Seau's brain underscored "the recognized need for additional research to accelerate a fuller understanding of CTE." NFL clubs have already committed a $30 million research grant to the National Institutes of Health.
Increased awareness and knowledge about brain injuries have unsettled the National Football League, a $9 billion a year industry. The league has attempted to institute rule changes protecting player safety while still preserving the spectacle that fans enjoy, which is partly based on the speed and power of the athletes colliding with one another.
Several thousand former NFL players have sued the NFL in federal court in Philadelphia, accusing the league of fraudulently concealing from players the risk of brain injury in playing professional football.
Just weeks before Seau shot himself, former Atlanta Falcons safety Ray Easterling committed suicide, and family members described a long descent into dementia following his retirement from the NFL. An autopsy revealed indications of CTE.
In February 2011, four-time Pro Bowl safety Dave Duerson, who played most of his career with the Chicago Bears, shot himself in the chest. In a suicide note, he donated his brain for study, and it was found to exhibit signs of CTE.
CTE, once known as boxer's dementia, is caused by repeated impacts to the brain, and has been found in athletes who suffered head injuries as well as members of the armed forces with concussive injuries from blast waves.
Because the mild and moderate brain injuries do not show up on CT scans or other imaging, the condition can be definitively diagnosed only through an autopsy.
(Reporting by Dan Whitcomb; Editing by Cynthia Johnston and Claudia Parsons)