The "American Idol" season eight runner-up announced the news on Twitter.
"Big News!!! I am going to be a judge on @thexfactor_au !!!" he wrote.
He will join newly-single Australian native Iggy Azalea and singer Guy Sebastian.
"I am very excited to join X Factor in Australia and am looking forward to helping people shine their brightest," Lambert said.
"Australia has always been one of my favourite places to tour. The Aussies I've met are so kind and good humoured - so the thought of getting to live in Sydney is exciting.