Abstract: An adjustable, portable truck bed assembly holder is disclosed herein. The holder includes a base structure and a retaining frame that is rotatably coupled thereto. The base structure includes a moveable chassis having opposing front and rear ends, a pair of vertical support posts extending upwardly from each of said the front and rear ends, a generally U-shaped center support member horizontally and rotatably displaced between said the upwardly extending free ends of the pair of vertical support posts. The retaining frame is attached to the center cross member, has a generally rectangular construction and includes a pair of retaining members, a pair of support members joined at the underside of said the retaining members, and securing flanges fixed to the retaining members. In an alternative embodiment of the truck bed assembly holder, the retaining frame includes retaining members which are expandable in the traverse direction of the center support member.