BACKGROUND: Problems with communication and team coordination are frequently linked to adverse events in medicine. However, there is little experimental evidence to support a relationship between observer ratings of teamwork skills and objective measures of clinical performance. AIM: Our main objective was to test the hypothesis that observer ratings of team skill will correlate with objective measures of clinical performance. METHODS: Nine teams of medical students were videotaped performing two types of teamwork tasks: (1) low fidelity classroom-based patient assessment and (2) high fidelity simulated emergent care. Observers used a behaviourally anchored rating scale to rate each individual on skills representative of assertiveness, decision-making, situation assessment, leadership, and communication. A checklist-based measure was used to assess clinical team performance. RESULTS: Moderate to high inter-observer correlations and moderate correlations between cases established the validity of a behaviourally anchored team skill rating tool for simulated emergent care. There was moderate to high correlation between observer ratings of team skill and checklist-based measures of team performance for the simulated emergent care cases (r = 0.65, p = 0.06 and r = 0.97, p < 0.0001). CONCLUSIONS: These results provide prospective evidence of a positive relationship between observer ratings of team skills and clinical team performance in a simulated dynamic health care task.