In the present generation wireless networks, mobile users are moving across various access technologies, using multi-interface terminalsand different types of services. In such a heterogeneous environment the most important issue is Always Best Connected (ABC) concept[1]. It allows the best connectivity to services anywhere any time. For that, a seamless inter-system handover solution is needed. One ofthe challenging problems for the vertical handoff is the decision for a mobile node to handoff between different types of networks. In thispaper we propose a multi-criteria vertical handoff decision algorithm for heterogeneous Wireless Wide Area Network (WWAN) andWireless Local Area Network (WLAN) environment. We have used an intelligent approach i.e. Fuzzy Logic Inference System for thedecision of handoff between the above two heterogeneous environment.