A pet litter tray, box and system. The litter box comprises multiple trays. The trays are nestable within one another. Each tray comprises a base defining one or more openings. The opening allows litter to pass therethrough. When stacked in a first orientation, the openings of each upper tray are blocked by portions of the base of the adjacent lower tray thus retaining the litter. The top-most tray is lifted to sift the unused litter into the two nested lower trays. The top-most tray is added to the bottom of the two nested trays in a selected orientation. The trays may comprise flanges extending from the openings to contact the base of the lower tray when stacked to retain litter. The trays may comprise protrusions extending from the rim to contact an adjacent lower tray to indicate improper orientation of the trays.
