Background: At a Midwestern academic medical center, we introduced a structured teamwork training program to cardiothoracic operating room members with a goal of greater than or equal to 90% reporting positive psychological safety after the program. Methods: We conducted teamwork training over 3 months. We distributed confidential questionnaires before the training, and then at 6 months and 12 months after the training. The primary outcome was the percentage of respondents reporting good or excellent psychological safety. Surveys were also distributed at the end of each case. Secondary outcomes were medical errors reported. Comparisons between percentages were evaluated with chi-square test. We examined the turnover of nurses and surgical technologists. Results: Positive psychological safety was reported by 57 of 73 (78.1%) at baseline and by 60 of 68 (88.2%) at 12 months (difference = 10.1%; 95% confidence interval, -2.4% to 23.4%; P =. 122). On the daily survey, 93.9% (n = 2786 of 2987) of operating room team members strongly agreed with the statement “I felt comfortable speaking up with questions and concerns” during the last quarter of the study. Reported medical errors decreased from 7.44% (n = 78 of 1048) in the first 6 months of the study to 4.65% (n = 55 of 1184) in the second 6 months (difference = 2.79%; 95% confidence interval, 0.8% to 4.8%; P =. 005). In 2015, 19 nurses of a pool of 40 (47.5%) left, followed by 7 (17.5%) in 2016 and 10 (25%) in 2017. Conclusions: Overall, the results of this study suggest that structured teamwork training in the cardiothoracic operating room environment has the potential to improve teamwork, psychological safety, and communication, and potentially also patient outcomes.