The Qatari club announced the deal on X, posting a photo of the 35-year-old Jamaica international in their shirt along with a video of his goals and training highlights. The length and financial terms of the contract were not disclosed.
Antonio left the Premier League side in August after the London club opted not to renew his contract.
He has not played club football since December 2024, when his car struck a tree as he drove home from training. The accident caused multiple fractures to his thigh, requiring surgery and more than three weeks in hospital.
He made his return to the pitch in June 2025 when he came on as an 85th-minute substitute for Jamaica in their 1-0 Gold Cup group stage defeat by Guatemala.
Antonio joined West Ham in 2015 and made 323 appearances, scoring 83 goals in all competitions. He is also the club's all-time leading Premier League scorer with 68 goals.