Abstract: An improved litter box assembly includes two litter boxes with one box nested within another. Each box has a floor with multiple openings and a plate disposed under the floor. Each plate is slidably attached to the floor of the respective box and also has multiple openings. The plate is slidable between a first position in which the openings in the floor and the openings in the plate correspond and a second position in which the openings in the floor are blocked by the plate. The boxes are identical and interchangeable. When nested, the boxes are reversed so that each plate, in sliding from the first position to the second position, slides in the opposite direction of the other plate in sliding from the first position to the second position. When the boxes are reversibly nested, a litter receiving space is created between the floors of the two boxes. In operation, when soiled litter in a upper box is to be removed, the plate of the upper box is moved from the first position to the second position.