A view of the design for the Minnesota Viking's new stadium released by the Vikings and posted to their website on May 13, 2013. (http://www.vikings.com)
The suit, filed in California Superior Court, blames the NFL for its "acts or omissions" that hid the dangers of repetitive blows to the head.
Seau died at age 43 of a self-inflicted gunshot in May 2012. Earlier this month, posthumous tests revealed that Seau suffered from chronic traumatic encephalopathy (CTE).
"Our attorneys will review it and respond to the claims appropriately through the court," NFL spokesman Brian McCarthy said in a statement.
The family is also suing Riddell, Inc., the manufacturer of NFL helmets, for its "negligent" design.
Seau spent 13 seasons with the Chargers, helping the franchise to their only Super Bowl appearance after the 1994 season. He also played three years for Miami and four more for New England before retiring after the 2009 campaign.