A pet life jacket includes a jacket body and a wearing mechanism. The jacket body includes a floatable back body, two floatable side wings sidewardly extended from the floatable back body, and two floatable collar arms frontwardly extended from the floatable back body. The wearing mechanism includes a belly lock provided at the floatable side wings and a collar lock provided at the floatable collar arms to form a floatable collar loop. The jacket body is adapted to be worn by a pet via the wearing mechanism at a position that the floatable back body is retained at a back of the pet, the floatable side wings are retained at two sides of the pet, and the floatable collar loop is encircled around a collar of the pet via the collar lock.