The deal will keep Turner with the Chargers through the 2013 season.
Turner, 57, has guided San Diego to three straight AFC West titles.
The Chargers lost 17-14 to the New York Jets Sunday in the divisional playoff round after compiling a 13-3 regular-season record.
"I'm extremely proud of the job Norv has done with this team," Chargers President Dean Spanos said Monday. "I'm confident that if we strengthen our roster and continue to provide Norv the assets he needs, this team will have continued success."
Turner has the top overall winning percentage in team history at .648 (35-19) as well as the top regular-season percentage (32-16, .667).