Abstract: The present invention relates to a vertically and horizontally collapsible truck bed cap including a planar platform attached to the truck bed adjacent the cab. Vertically depending from the upper surface of the platform are a plurality of extendable hydraulic cylinders which support a rigid cover member. The cover member has a substantially inverted U-shaped vertical cross section with top and front walls and two parallel spaced side walls vertically depending therefrom which rest on the hydraulic cylinders. A canopy member is received within the cover member a portion of which is peripherally attached thereto while the remaining portion is extendable therefrom. The canopy is supported in an extended or retracted position by a frame structure including a plurality of spring loaded, horizontally telescoping rods attached to the cover member front wall. The rods may be locked in a retracted position by a release button and key lock mechanism in communication therewith.