An absorbent article for pet configured to be worn in a state of being wrapped around a waist of a pet, the absorbent article for pet comprising: a top sheet having a liquid permeable nonwoven fabric; a liquid impermeable back surface layer; an absorbent core disposed between the top sheet and the back surface layer; a first end portion and a second end portion opposing to each other in a longitudinal direction of the absorbent article for pet; a pair of side portions opposing to each other in a width direction of the absorbent article for pet; a hook member disposed along the width direction of the absorbent article for pet on a top sheet side in the vicinity of the first end portion; a pair of side sheets (51, 52), which is disposed on the top sheet side of the pair of side portions, an outer edge of which is joined with the top sheet or the back surface layer and at least a part of an inner edge of which is a free end; a first engaged portion (21, 21 A) that is provided on a back surface layer side in the vicinity of the second end portion and engageable with the hook member; and a pair of folding lines extending in the longitudinal direction of the absorbent article for pet; characterized in that said absorbent article further comprises: a second engaged portion provided on the top sheet side in the vi cinity of the first end portion on each of outer sides of the pair of folding lines in the width direction of the absorbent article for pet, the second engaged portion being engageable with the hook member with an engagement force smaller than an engagement force of the top sheet with the hook member, in a state in which the pair of side portions are folded back from the pair of folding lines and the second engaged portion covers at least a part of the hook member, wherein the inner edges of the pair of side sheets (51, 52) are positioned inward of the pair of folding lines in the width direction of the absorbent article for pet. a top sheet having a liquid permeable nonwoven fabric; a liquid impermeable back surface layer; an absorbent core disposed between the top sheet and the back surface layer; a first end portion and a second end portion opposing to each other in a longitudinal direction of the absorbent article for pet; a pair of side portions opposing to each other in a width direction of the absorbent article for pet; a hook member disposed along the width direction of the absorbent article for pet on a top sheet side in the vicinity of the first end portion; a pair of side sheets (51, 52), which is disposed on the top sheet side of the pair of side portions, an outer edge of which is joined with the top sheet or the back surface layer and at least a part of an inner edge of which is a free end; a first engaged portion (21, 21 A) that is provided on a back surface layer side in the vicinity of the second end portion and engageable with the hook member; and a pair of folding lines extending in the longitudinal direction of the absorbent article for pet; characterized in that said absorbent article further comprises: a second engaged portion provided on the top sheet side in the vi cinity of the first end portion on each of outer sides of the pair of folding lines in the width direction of the absorbent article for pet, the second engaged portion being engageable with the hook member with an engagement force smaller than an engagement force of the top sheet with the hook member, in a state in which the pair of side portions are folded back from the pair of folding lines and the second engaged portion covers at least a part of the hook member, wherein the inner edges of the pair of side sheets (51, 52) are positioned inward of the pair of folding lines in the width direction of the absorbent article for pet. a second engaged portion provided on the top sheet side in the vi cinity of the first end portion on each of outer sides of the pair of folding lines in the width direction of the absorbent article for pet, the second engaged portion being engageable with the hook member with an engagement force smaller than an engagement force of the top sheet with the hook member, in a state in which the pair of side portions are folded back from the pair of folding lines and the second engaged portion covers at least a part of the hook member, wherein the inner edges of the pair of side sheets (51, 52) are positioned inward of the pair of folding lines in the width direction of the absorbent article for pet.