An absorbent article for pet to be worn and wrapped around a waist thereof, includes: a liquid permeable top sheet; a liquid impermeable back surface layer; an absorbent core; a first end portion and a second end portion opposing to each other; a first side portion and a second side portion opposing to each other, a first gather portion that is disposed on a top sheet side of the first side portion and configured to stand upright from the top sheet; a second gather portion that is disposed on the top sheet side of the second side portion and configured to stand upright from the top sheet; and a pair of releasably-joined portions in which the first gather portion is releasably-joined to itself in a state of being folded outward in the width direction of the absorbent article for pet, in the first end portion and the second end portion.