An expandable trailer vehicle is provided. The trailer vehicle comprises a wheeled vehicle frame that is adapted to be towed by a towing vehicle. The vehicle frame supports an expandable trailer structure having a front and rear wall, a floor, and a roof. The trailer structure includes expandable sections from the sides thereof, whereby a pair of L-shaped expandable side sections pivots outward from the sides of the trailer structure and form the floor and outer walls when deployed. Pivoting sidewalls pivot forward and rearward from the sides of the trailer structure to form the front and rear walls of the expanded section, closing out the L-shaped side sections when in a deployed state. A pair of side section roof surfaces extends from the roof of the trailer vehicle to close off the upper surface of the L-shaped side sections when in a deployed state.