A combination storage unit/auxillary bed liner assembly is adapted for nesting engagement onto the bed of a pickup truck. The storage unit covers the entire open area of the pickup bed, with the space between the auxillary bed liner and the truck bed being partitioned to provide multiple storage compartments. A top-opening auxillary storage compartment is formed on each side of the two rear wheel well regions. Two pull-out drawers are received within adjoining central compartments and extend substantially the entire length of the truck bed. The pull-out drawers provide secure storage compartments for tools and equipment, and also serve as work tables. The auxillary cargo deck liner is supported by interior side panels, a central partition and engagement of saddle/bridge deck portions onto wheel well flanges.