The Chargers agreed to terms Friday on a two-year contract with Whitehurst and released fellow quarterback Billy Volek.
Whitehurst was selected by San Diego in the third round -- No. 81 overall -- of the 2006 NFL Draft but was traded to the Seattle Seahawks prior to the 2010 season.
He has only thrown passes for the Seahawks in his six-year career, completing 84-of-155 attempts for 805 yards and three touchdowns over two seasons. He had two rushing attempts as a third-stringer for the Chargers in 2006, gaining 13 yards with a TD.
Volek, a 12-year veteran, had backed up starter Philip Rivers. He spent five- plus seasons on the Chargers.