Cognitive radio is an emergent technology in wireless networks that aims to improve spectrum’s use by allowing opportunist access. Recent research activities related to cognitive radio consider static terminals, neglecting the impact of user’s mobility. In this paper, we are interested in the concept of mobility in cognitive radio networks. Thus, we propose an algorithm of spectrum handoff for mobile cognitive radio users. Our algorithm presents a decentralized approach using multi-agent systems. Each terminal is managed by an agent that enables it to negotiate and cooperate with neighboring users. During the handoff, agents recover sensing information then choose appropriate band to switch if spectrum handoff is necessary. Finally, agents use negotiation and cooperation methods to insure a more efficient spectrum sharing.