To provide a disposable diaper for pets that fits well around the waist of the pet. A disposable diaper for pets, having: a diaper longitudinal direction (Y)； a diaper longitude-intersecting direction (X)； a rear-side flap section (160)； a stomach-side flap section (150)； and a tail insertion opening (190) provided in a prescribed area in the diaper longitudinal direction (Y). The disposable diaper for pets is formed such that the length (160L) in the diaper longitude-intersecting direction (X) in the rear- side flap section (160) is different from the length (150L) in the diaper longitude-intersecting direction (X) in the stomach-side flap section (150).
