The Republic of Ireland international has officially completed a move to Wearside, penning a three-year contract with the Black Cats.
He arrives on a free transfer, having allowed his contract to run down at Coventry, but has forged quite a reputation during his time in the Championship.
At 26 years of age he could be a key figure for Sunderland in the years to come, with Steve Bruce's transfer activity this summer keeping one eye on the future.
Westwood hopes he can be a success at the Stadium if Light and has no plans to play back-up to Craig Gordon or Simon Mignolet - having already tasted disappointment once in his career.
"Getting released by [Manchester] City as a 19-year-old was the kick up the backside I needed," he said.
"It gave me the hunger and desire to prove a lot of people wrong.
"I've come here to play first-team football. I know it'll be a tough contest with the other lads who are vying for the shirt and it's all about competition."
Sunderland have also wrapped up a deal for former Birmingham midfielder Sebastian Larsson, with the Swede having penned a three-year contract of his own.
He is another new recruit who will be looking to make an immediate impact next season, with the Black Cats setting their sights on a top-six challenge in 2011/12.
Larsson said: "This is a huge club with big ambitions and it's heading in the right direction.
"I'm looking forward to working with the manager again."