The presenter, who came close to signing for the broadcaster last year, has accepted a three-year-deal to be the face of ITV1's football coverage, according to People.
Chiles had looked poised to quit the BBC following the corporation's decision to hire Chris Evans to front The One Show on Friday evenings, alongside Christine Bleakley.
"This is a massive signing for us. Adrian is a top talent and the public love his style," an ITV source revealed. "We were quite frankly staggered by the way the BBC treated him and made an immediate offer, which we're delighted he's accepted. This is a real coup for ITV."
Another insider explained the 43-year-old's decision: "Adrian doesn't want to fall out with the BBC but he has been hurt by the way the BBC seems to have gone out of its way to try and relaunch the TV career of Chris Evans while putting The One Show's reputation at risk.
"He has built up an audience from nothing to more than 6 million, five nights a week and really knows his audience. Chris Evans is taking over, as he did with Wogan on Radio 2, a ready-made following."
The source added: "Adrian has absolutely nothing against Chris Evans but feels he should be launching his own show rather than gatecrashing someone else's show which is already successful.
"Adrian feels it is better to leave now while The One Show is at the top rather than hang around to see what happens. He's excited by the opportunities at ITV. They desperately want him as their big new star and that says something about their foresight."