As global projects get more complex, virtual teams are established to bring together experts from different fields and cultures. Challenged by different work habits and communication patterns, these teams need fast and effective assessment of their teamwork to install efficient adjustments. In this chapter, the authors introduce an assessment for virtual teamwork based on the virtual team maturity model (VTMM®). The model focuses on internal team processes necessary to compensate for missing face-to-face communication. The VTMM® model defines meta-processes that help create a highly motivated virtual project team, leading to trust, cohesion, and consequently, an improved team performance. In a case study, the authors examine the effects of an VTMM® assessment and implementation of corresponding measures for improvement on virtual team performance. The outcomes are compared to the results of a recent survey on success and failure in virtual team maturity implementation, where project managers from different backgrounds and experience reported their practical observations.