An absorbent article for pet includes: a liquid permeable top surface layer, a liquid impermeable back surface layer, and an absorbent core disposed between the top surface layer and the back surface layer; the absorbent article for pet being configured to be in a belt-like shape and to be fit wrapped around a waist of a pet, in which the absorbent core includes: a belt-like absorbent core main body that extends from the first end portion side to the second end portion side in the longitudinal direction LD of the absorbent article for pet; and a first extension portion that extends outwards in a width direction from a first side edge in a central portion in the longitudinal direction of the absorbent core main body.