A retractable leash for dogs and other pets. A casing is fastened to a dog collar and remains connected thereto during periods when the animal is not being walked. A rotatable reel is supported in the casing and a flexible leash is wound about the reel. One end of the leash is externally accessible of the casing by connection to a handle. A spring engages both the reel and the casing and tightly coils in response to the unwinding of the leash. A removable cover on one side of the casing facilitates servicing, the cover being locked closed by the attachment to the animal's collar.