Bent has signed a four-and-a-half year contract and will make his debut in Saturday's home Barclays Premier League clash with title-chasing Manchester City.
It is the third big money move of his career after moving from Charlton to Tottenham for £16.5million and then an initial £10million from Spurs to the Black Cats.
Bent said: "When I first went to Spurs, and it happened there (moving for a big transfer fee), I was so nervous.
"It did play a massive part in my mind and it probably got me down at times. But I'm older and more wise now.
"I've played a few more seasons in the Premier League and it just comes with the territory now."
Source: PA
Source: PA