This study investigates how 3D virtual worlds (3DVWs) support team collaboration. Based on Media Synchronicity Theory, we pose that the shared environment and avatar-based interaction allowed by 3DVWs aid convergence processes in teams working on a decision making task, leading to increased shared understanding between team members. This increases performance of decision making teams. An experiment was conducted in which 70 teams of 3 participants had to decide on a spatial planning issue. The teams interacted using synchronous text-based chat, a 3D virtual decision room, or were present in the virtual environment mirroring the spatial planning task. Results revealed that in both the virtual decision room and the virtual environment shared understanding was higher than in the text-based chat condition. This led to higher task performance in terms of consensus, satisfaction, and cohesion. Our results show that 3DVWs offer potential for team collaboration over more traditional text-based collaboration technologies.