Future wireless networks will allow users to seamlessly roam among heterogeneous wireless networks. To provide services anywhere and anytime in such a diverse networking environment, vertical handoff is still a crucial target. In this paper we propose non-real time services vertical handoff decision algorithm NRS-VDA. NRS-VDA is an intelligent vertical handoff decision algorithm that can manage efficient vertical handoff initiation and decision procedure between UMTS and WL AN networks. NRS-VDA ensures the avoidance of unnecessary and detrimental vertical handoffs and provides high throughput and low blocking probability. NRS-VDA is defined for upward and downward vertical handoff scenarios. The proposed algorithm takes several metrics into account such as velocity of mobile terminal, bandwidth, and Received Signal Strength (RSS) of the network. It is suggested that NRS-VDA will improve the overall efficiency of vertical handoff in Next Generation Networks (NGN). © 2010 IEEE.