Whitehurst signed his restricted free-agent tender Wednesday so the trade could be completed, a source said.
"Big, talented, athletic guy with a strong arm and a competitive streak," said Seahawks general manager John Schneider. "We believe he has the potential to be a successful quarterback in this league."
San Diego and Seattle swapped second-round choices in this year's draft, with the Chargers moving up 20 slots in the process, getting the 40th overall choice while giving up the 60th choice. In addition, San Diego receives an undisclosed 2011 draft choice from Seattle.
"We are all about competition," said Seahawks head coach Pete Carroll. "Charlie has tremendous talent and upside and we are very excited to watch him develop and help our football team."
Whitehurst, from Clemson University, was originally a 2006 third-round draft choice by San Diego where he spent the last four seasons. After serving as the backup in 2006, he has been inactive each of the last three years as the third quarterback. In 2006, he saw action in two games with no passes attempted. Versus Tennessee that season, he replaced Phillip Rivers late in the fourth quarter and scored his first-career NFL touchdown on a 14-yard run.
He finished his collegiate career with 25 wins, second-best total in school history, and earned second-team All-ACC as a senior in 2005. Among his win total were eight fourth quarter come-from-behind victories, seven wins over top-25 teams and three wins versus top-10 teams. He graduated with 46 school records, including career passing yardage, completions, touchdown passes, completion percentage and 300-yard games.
Whitehurst's father, David, is also a former NFL quarterback. He played for Green Bay from 1976-83.
The trade leaves Philip Rivers and Billy Volek as the two remaining quarterbacks on the Chargers' roster.
While the Seahawks are believed to have paid veteran QB Matt Hasselbeck his $1 million roster bonus earlier this month, it would make sense to believe that Whitehurst will be given a chance win the starting job in training camp considering what the team gave up to get him.
Whitehurst trade official
CUTigers.com Top Stories
RECRUITING RADAR: ACC CHAMPS!In our weekly Recruiting Radar, CUTigers Recruiting Analyst Gary McDaniel updates you on the latest news and intel on the Clemson recruiting front!
CUTigers.comYesterday at 3:12 PM
SPECIAL OFFER: 15% OFF FIESTA BOWL TICKETS!NOW THROUGH MIDNIGHT WEDNESDAY ONLY: 10% ticket discount for CUTigers.com Premium Members is increased to 15%!
CUTigers.comMonday at 12:33 PM
ACC CHAMPIONSHIP POST-GAME INTERVIEWSWatch Dabo Swinney, Deshaun Watson and more Clemson coaches and players discuss their second consecutive ACC Championship on Saturday night!
CUTigers.comSunday at 11:18 AM
PLAYOFF REPEAT FOR TIGERS#2 Clemson will join Alabama as the only two programs to make repeat trips to the College Football Playoff.
CUTigers.comSunday at 10:10 AM
ANOTHER CLEMSON CHAMPIONSHIP!!!#3 Clemson held on to beat #23 Virginia Tech 42-35 for its first back-to-back ACC Titles in 28 years.
CUTigers.comSaturday at 11:52 PM