The performance of an unmanned aerial vehicle (UAV) assisted energy harvesting cognitive radio (CR) network is studied in this paper. The UAV is a CR enabled device, rotates around a primary user (PU) at a certain height for sensing the PU channel and forwards the information of a CR source to the corresponding CR destination in absence of PU. One rotation period of the UAV is divided in three sub-periods: harvesting period, sensing period and transmission period. The functionalities (sensing and information forwarding) of the UAV depend on the harvested energy from radio frequency (RF) signal of the CR source while a dedicated battery is used to take care of its mobility. The performance of the UAV is investigated for two schemes: (i) without cooperation of the ground node and (ii) with cooperation from the ground node. Novel analytical expressions for the overall sensing decisions, and throughput are developed. The performance is investigated in terms of false alarm, detection probability and throughput for several parameters such as velocity of CR, and radius of the UAV trajectory. © 2020 IEEE.