A convertible sidewall extender to truck bed cover assembly includes a pair of panels that each has an outside edge. Each outside edge is hingedly coupled to a respective side rail of a truck bed. Each of a plurality of doors is hingedly coupled to a respective panel, such that the door is positioned to cover a respective opening in the respective panel. The doors are configured to allow access to the truck bed. Each of a plurality of support rods is positionable between the pair of panels proximate to inside edges of the pair of panels. The support rods are positionable to support the pair of panels in an open configuration where the pair of panels is in substantial parallelism with the side rails of the truck bed.