Projects are commonly used within organizations to deal with complex tasks and improve organizational performance. However, the overall project success rate is relatively low and it is still difficult to effectively manage project teams for achieving project success. Diverse results which suggested different relationships between key factors and project team outcomes were found in the literature. This study identified key factors which are most strongly related to project team performance and determined their relationships with project team outcomes. The purpose is to help organizations and researchers effectively manage project team performance. Meta-analysis was used to identify key factors affecting project team performance and estimate their effect size. Data were collected from 133 project teams by using a survey questionnaire which measured the characteristics and outcomes of project teams. The correlations between input/process factors and outcome factors were calculated to identify the relationships. The average correlations between factors were compared with the effect size obtained from meta-analysis. The results found that the correlations of Management Support, Team Diversity, Communication, Cohesion, and Commitment were consistent with the findings from previous project team studies, while the other variables had higher correlations in this study than in previous studies. Copyright, American Society for Engineering Management, 2012.