A litter box assembly is provided that includes a tray for containing litter and a shield that can be removably mounted to the tray for reducing or preventing the scattering of litter material outside the tray. The shield effectively extends the height of the tray along three sides and can be removed for cleaning between litter changes. A self supporting shield for a litter box tray is further provided as well as a method for reducing the scattering of litter material by a cat or other animal.