The X Factor star topped the public vote ahead of rival finalist Cheryl Baker to emerge victorious from the second series of the ITV singing contest.
The 20-year-old won viewer support after performing alongside Popstar to Operastar mentor Rolando Villazón and belting out a final solo piece earlier tonight.
He later took to the stage with Baker, Villazón and show judge Katherine Jenkins just before phonelines closed.
With the result revealed, McElderry enthusiastically hugged Baker and appeared to be more concerned with the Bucks Fizz star's reaction to her loss rather than his big win.
"I've had an absolute blast with Cheryl," he told show host Myleene Klass. "I love her to bits."
However, Baker insisted that she was happy for McElderry and admitted that she had always tipped him to take the title.
"I didnt expect to get this far and he's fantastic," she said. "I had my money on Joe from the beginning."
McElderry later took to Twitter to celebrate his victory, writing: "Wooop!!!! We did it!!!!! Thankyou soo much to everyone that voted!!!!! Soo exited and happy!!!!!!! (sic)".
McElderry found fame by winning the sixth series of The X Factor in December 2009.
He was dropped from Simon Cowell's record company Syco in April, but hinted this weekend that he may soon be releasing a second studio album.