Abstract: A collapsible boom and derrick hoist assembly, including a base frame securable to the side rails of a conventional pickup truck. A collapsible A-frame supports a foldable, two-piece boom assembly. A boom swing mechanism includes a gear driven arrangement for rotating the boom or yawing the boom about its vertical axis. A boom elevating mechanism including a winch, cable, and a pivotally supported pulley permits elevation of the erected two-piece boom with the elevation angle remaining constant as the boom swings about its vertical axis. An A-frame erection subassembly including a strut arrangement for obtaining a mechanical advantage is provided along with a boom erection and winching cable arrangement. A plurality of screw jacks are pivotally connected to side members of the base frame and serve to support the derrick hoist assembly and stabilize the assembly during operation.