Abstract: A modular, multi-level pet housing that comprises a plurality of multi-sided boxes. A top and bottom is provided for each box. A plurality of tubular columns of a first length generally less than the height of the side walls and a plurality of tubular columns of a second length generally longer than the height of the side walls are provided. The tubular columns may be joined to each other by a coupling member. The top and bottom of each box is formed with a hole adjacent each corner that is sized to selectively permit one of the tubular members to fit therethrough, but to prevent an associated sleeve member from fitting therethrough.