The 18-match season-ticket package includes 15 regular-season matches and three international friendlies to be played at Qwest Field.
"Our fans demonstrated their passion and commitment to the team by creating one of the best home-field advantages in all the MLS," said Sounders FC owner Joe Roth. "They took their match-day role very seriously and renewed their season tickets at a 96 percent rate."
In their inaugural season, the Sounders capped season tickets at 22,000.
They will host Philadelphia Union in the 2010 MLS First Kick on March 25 to be broadcast live on ESPN2.