Washington athletic director Scott Woodward announced the decision following an afternoon team meeting. Tuiasosopo was Washington's quarterbacks coach this past season and met with Woodward earlier in the day when he was offered the interim job.
"I'm humbled and so honored," Tuiasosopo said in an announcement from the school. "It's a great, incredible honor to lead my alma mater in a bowl game. We still have a lot to play for this season. I am excited to go out and get a ninth win."
The 34-year-old Tuiasosopo was a star quarterback at Washington from 1997-2000, leading the Huskies to a Rose Bowl title after the 2000 season.
Tuiasosopo spent the 2012 season on the coaching staff of Jim Mora at UCLA as an assistant tight ends coach before returning to Seattle last year to take the role of coaching Washington's quarterbacks.
Tuiasosopo spent parts of six seasons in the NFL playing for the Oakland Raiders. His first venture into coaching came in 2010 when he joined the staff at Washington as an assistant strength coach.
The decision to elevate Tuiasosopo to the interim job does leave in question the status of defensive coordinator Justin Wilcox, who was thought to be a potential permanent replacement following Sarkisian's departure.
There's been talk that Sarkisian wants Wilcox to join him at USC. But Wilcox's contract with Washington includes a $1 million buyout if he leaves for another conference school.
"Whatever decision is made we're going to roll with it," Washington quarterback Keith Price said earlier this week. "We're going to perform at the best of our abilities."
The Huskies are expected to return to practice later this week in preparation for their bowl game. No bowl announcement is expected until Sunday, although the Kraft Fight Hunger Bowl in San Francisco seems to be the front-running destination.
Washington is coming off its best season since 2001 winning eight games in the regular season with a chance at a ninth win in the bowl game.