The purpose of this study was to examine the exercise beliefs of breast cancer survivors before and after participation in a randomized trial. Prior to randomization, 52 breast cancer survivors completed exercise belief measures based on the theory of planned behavior. After the trial, participants assigned to the exercise group (n = 24) completed the belief measures again. Results show that there was significant variability in the expected benefits of exercise prerandomization, ranging from 40% for a reduced risk of breast cancer recurrence to 94% for an improved energy level. Moreover, attitudes toward exercise and perceptions of control were higher in the exercise group after the exercise program. The findings are discussed in terms of the veracity of the exercise beliefs held by breast cancer survivors as well as the aspects of the program that may have contributed to the positive changes in exercise beliefs.