The Take That star, who mentored Marcus Collins to the runner-up spot on last year's show, is the first judge confirmed for the 2012 series.
"I'm thrilled to be back and really looking forward to working with the X Factor team again," said Barlow.
"The fact that a superstar could just walk out on that stage is very exciting."
Show boss Simon Cowell claimed that Barlow has "earned his place" on the panel and said that was "excited" to be working alongside Barlow again.
ITV's director of television Peter Fincham said: "Gary quickly established himself as a key member of The X Factor judging panel, drawing on his years of experience in the music industry to help in the search for our undiscovered singing stars.
"I'm thrilled to welcome him back to the biggest show on British television."
Tulisa Contostavlos and Louis Walsh are also expected to be back on the Saturday night show when it returns; however, Kelly Rowland's spot on the panel appears to be hanging in the balance.
Richard Holloway from X Factor producers Thames said: "Gary brings his vast music expertise, his fabulous character and down-to-earth approach to the show and audiences adore him so we are absolutely delighted that he's coming back."
X Factor's open auditions tour around the UK has finished, although hopeful singers can still apply via Facebook until May 8.
A new twist to the show's format means that any artist or act, aged 16 or above, can apply for the show, even if they have a management deal.
The three other judges will be announced soon ahead of the spring auditions tour. The X Factor will air again in the late summer on ITV1.
> Louis Walsh self-confirms his 'X Factor' return
> Simon Cowell to be 'Voice of God' via Skype for 'X Factor'
Watch Gary Barlow discuss his desire to return to The X Factor earlier this year below: