Background: Up to 60% of adverse events in surgery are the result of poor communication and teamwork. Nontechnical skills in surgery (NOTSS) are critical to the success of surgery and patient safety. The study aim was to evaluate the effect of a brief team training intervention on teams' observed NOTSS. Methods: Pretest-posttest interrupted time-series design with statistical process control analysis was used to detect longitudinal changes in teams' NOTSS. We evaluated NOTSS using the revised NOTECHS weekly for 20 to 25 weeks before and after implementation of a team training program. Results: We observed 179 surgical procedures with cardiac, vascular, upper gastrointestinal, and hepatobiliary teams. Mean posttest NOTECHS scores increased across teams, showing special cause variation. There were also significant before and after improvements in NOTECHS scores in respect to professional role and in the use of the Surgical Safety Checklist. Conclusions: Our results suggest associated improvements in teams' NOTSS after implementation of the team training program. Key Words: teamwork, intervention, patient safety, operatin