The present invention relates to a reusable outer sleeve that is made of durable material for the purpose of protecting the sidewalls and corners of a fully-disposable pet toilet unit that incorporates living grass as an absorbent material for the bodily waste of pets. The sleeve eliminates or minimizes damage that can be caused by pets who engage in biting, chewing, gnawing, clawing, pecking, ripping and/or tearing of the apparatus. When the cover of a disposable pet toilet unit is removed by the user following the units delivery, the bottom of said unit is placed within the sleeve before the pet uses the toilet for the first time. The bottom of the unit is removed from the sleeve when it is time to discard the disposable pet toilet. The sleeve is retained for future use with other disposable pet toilet units that fit within the sleeve.
