McClean has signed a new contract to keep him at the Stadium of Light until the summer of 2015.
"I'm thrilled to be here. I'm really enjoying my football and to have earned a new contract is a dream," he told the club's official website.
"I'm over the moon to see my next three years with Sunderland."
O'Neill added: "I'm absolutely delighted that James has committed himself to the club.
"He's had an explosive start to his career here at Sunderland and long may it continue."