According to Reveal magazine, the former X Factor judge is giving the Black Eyed Peas star tips and support ahead of this weekend's first live episode.
The show is expected to be seen by over 10 million viewers on Saturday night, as Will and Sir Tom Jones' artists sing for the first time.
"She's giving him advice on everything from his manner to his appearance," a source blabs.
They went on: "She told him to cut back on the name-dropping, as it may work in America but it doesn't go down well over here. And she's given him loads of tips on how to adjust his performance for a British audience.
"Cheryl's also suggested that he should show more empathy and not be afraid of showing emotion on the show. And she's delighted with the results."
The source added that Cheryl cheekily told Will that her biggest tip was for him "not to be like Simon [Cowell]!"
It's been speculated that Cheryl, who is managed by Will.i.am, could be performing on the live shows later this year.
The Black Eyed Peas star told us previously that if Cheryl was up for it, it would happen.
And with her new single Call My Name is out in June, the live shows of The Voice UK are the perfect time to promote the song.
Watch this space...