Disruptions in surgical flow have the potential to increase the occurrence of surgical errors; however, little is known about the frequency and nature of surgical flow disruptions and their effect on the etiology of errors, which makes the development of evidence-based interventions extremely difficult. The goal of this project was to study surgical errors and their relationship to surgical flow disruptions in cardiovascular surgery prospectively to understand better the effect of these disruptions on surgical errors and ultimately patient safety. A trained observer recorded surgical errors and flow disruptions during 31 cardiac surgery operations over a 3-week period and categorized them by a classification system of human factors. Flow disruptions were then reviewed and analyzed by an interdisciplinary team of experts in operative and human factors. Flow disruptions consisted of teamwork/communication failures, equipment and technology problems, extraneous interruptions, training-related distractions, and issues in resource accessibility. Surgical errors increased significantly with increases in flow disruptions. Teamwork/communication failures were the strongest predictor of surgical errors. These findings provide preliminary data to develop evidence-based error management and patient safety programs within cardiac surgery with implications to other related surgical programs.