The Voice UK judge, who has collaborated with Cheryl and has previously managed her, said he was "proud" of the Girls Aloud star for making a comeback.
Cheryl left The X Factor UK for its US version in 2011, but only lasted three weeks before being replaced by then-presenter Nicole Scherzinger.
Speaking on Alan Carr: Chatty Man, which will air tonight (4 April), will said: "Do you know how strong you have to be to go back and do that? One, so hats off and applause and salute you for finding the strength to go back after that happened to you.
"Second, the reason is because she's experienced a lot and has a lot of wisdom and experience to give to these people who want to sing and aspire to be like Cheryl and have a strong background and thick skin to overcome and do the impossible.
"So hats off to you for that. And you can guide these kids and singers who want that platform and compete, and you have a lot of knowledge to exchange through your experience, the heartaches and the pains, and I'm proud of her for that."
This isn't the first time that will has spoken about Cheryl's now-famous dismissal. In April last year, will spoke about the moment he confronted music mogul and X Factor boss Simon Cowell over Cheryl's axe.
The 39-year-old Black Eyed Peas star explained: "With the incident that happened with Cheryl, I was like, 'Hey Simon, Cheryl asked me to manage her, I have to fight for her, but I hope it doesn't change how you view me as an artist'."
Watch will.i.am talk about The X Factor, judging on The Voice UK and see an exclusive clip from his brand new song 'It's My Birthday' on Alan Carr: Chatty Man tonight at 10pm on Channel 4.
Got an iPad or iPhone? Reveal Mag has been especially designed to fit!