Objective: We sought to determine whether preoperative and postoperative anxiety, depression, and stress symptoms were associated with atrial fibrillation (AF) after cardiac surgery. Methods: Two hundred and twenty-six cardiac surgery patients completed measures of depression, anxiety, and general stress before surgery, and 222 patients completed these measures after surgery. The outcome variable was new-onset AF, confirmed before the median day of discharge (day 5) after cardiac surgery during the index hospitalization. Results: Fifty-six (24.8%) patients manifested incident AF, and they spent more days in hospital (mean [M], 7.3; standard deviation [SD], 4.6) than patients without AF (M, 5.5; SD, 1.4; P