An absorbent article for pets includes a top surface layer, a back surface layer, and an absorbent body, and is formed in a rectangular shape having opposing first and second end portions, and a pair of opposing side portions that are perpendicular to the first and second end portions, The top surface layer side of the first end portion is arranged on the body of the pet, and the top surface layer side of the second end portion is detachably attached to the back surface layer side of the first end portion when worn. The absorbent article includes a rectangular engaging member arranged on the back surface layer side of the first end portion; and a pair of folding line portions formed on the first end portion and constituting a point where the pair of opposing side portions begin to curve towards the front surface layer side.