Purpose: This study investigated the use of private prayer among middle-aged and older patients as a way of coping with cardiac surgery and prayer's relationship to optimism. Design and Methods: The measure of prayer included three aspects: (a) belief in the importance of private prayer, (b) faith in the efficacy of prayer on the basis of previous experiences, and (c) intention to use prayer to cope with the distress associated with surgery. The sample was 246 patients awaiting cardiac surgery. The first in-person interview was administered 2 weeks before surgery and optimism was measured the day before surgery by telephone. Results: Private prayer predicted optimism, along with older age, better socioeconomic resources, and healthier affect. Neither measures of general religiosity nor any type of prayers used by patients were associated with optimism. Implications: Suggestions were made for clinicians to improve spiritual assessment and care, and for researchers to address spiritual coping in clinical situations.