A foldable cushion includes a cushion mechanism and a connecting mechanism. The cushion mechanism includes a seat unit and a back unit. The seat unit and the back unit are juxtaposed and movable relative to each other along a transverse folding line. The connecting mechanism includes a first endless cord and a second endless cord. The first endless cord and the second endless cord respectively extend through the transverse folding line and are flexibly arranged on the seat unit and the back unit. When the seat unit and the back unit are moved relative to the transverse folding line, the first endless cord and the second endless cord are stretched, so that the seat unit and the back unit are positioned at an expanded state by the elastic force of the first endless cord and the second endless cord.