Officers were called to Shaftsbury Avenue, Intake, Doncaster, just before 8am on Sunday (May 22) to reports of an out of control dog.
A 77-year-old man was bitten on his hand and arm.
The dog, a male German Shepherd, has now been seized by officers – but officers are still trying to locate its owner.
Anyone with information should call 101 and quote incident number 752 of May 22.