After the show’s low ratings in 2011, show producers hope Dixon will attract more viewers to the televised talent show.
The three new judges will also be joined by Britain’s Got Talent regular Amanda Holden.
”I am delighted to be joining the judging panel of Britain’s Got Talent for 2012,” Dixon said. ”It’s a fantastic show and I am very excited to be working with Simon, David and Amanda on the search for a new star.”
Cowell was also delighted with his new recruit.
“I love Alesha. She is feisty, opinionated and knows what it’s like to be both a competitor and judge on a hugely popular TV show,” he said.
Dixon, 33, is said to be receiving £350,000 for her new job – believed to be three times her Strictly salary estimated at £100,000.
She rose to fame in urban band Mis-Teeq, then won Strictly as a contestant in 2007 before becoming a judge on the show.
The winner of the show can look forward to a £500,000 cash prize – £400,000 more than usual.