Wireless environment is expected to support heterogeneous wireless access technologies. The objective is the support of a diverse range of high-data rate multimedia services. The main issue in this environment is to provide a seamless vertical handoff mechanisms, which allow mobile users to handoff transparently from access technology to another. In this paper we propose a distributed handoff decision scheme to enhance service mobility using the Simple Additive Weighting (SAW) method in a distributed manner, under heterogeneous environments. Our main goal is to reduce the overload and power consumption in the mobile terminal, by delegating the calculation of handoff metrics for network selection to the Visiting Networks.