Anxiety can contribute to poor prognosis in cardiac patients. Few studies have examined the role of optimism in anxiety after open heart surgery (OHS). This study investigated the influence of preoperative optimism on post-OHS anxiety, adjusting cardiac indices used by cardiac surgeons. Data were collected before and 1 month after OHS in 481 patients (58% men; age, 62.4 ± 11.94 years). Optimism was measured using the Life Orientation Test. Anxiety was measured using the Trait Anxiety Inventory. Medical and cardiac indices were retrieved from the Society of Thoracic Surgeon's national database. Multiple regression analyses showed that greater pre-OHS optimism was associated with lower levels of post-OHS anxiety (F[6, N = 306] = 50.18, p < 0.001, R = 0.502). No other factors showed similar protection. Pre-OHS anxiety, younger age, and minority status were associated with anxiety in the critical recovery month. The findings demonstrate the potential benefit of optimism against post-OHS anxiety, which may have clinical implications for improving disease management.