The demand for increased data transfer rate and network traffic capacity has given rise to the concept of heterogenous networks. Heterogeneous networks are wireless networks, consisting of devices using different underlying radio access technologies (RAT). In an urban heterogeneous network environment, Unmanned Aerial Vehicles (UAVs) must be able switch seamlessly from one base station to another for maintaining a reliable link. Therefore, seamless handover in such environments have become a major challenge. In this paper, a novel scheme to achieve seamless handover is developed, an algorithm based on Received Signal Strength (RSS) criterion for network selection is used and Entropy Weighted Property (EWM) is implemented for decision making. Seamless handover using EWM decision-making is demonstrated successfully for a UAV moving across fifth generation (5G) and long-term evolution (LTE) networks via a simulation level analysis. Thus, a solution for UAV-5G communication, specifically the mobility challenge in heterogeneous networks is solved and this work could act as step forward in making UAV-5G architecture integration a possibility.