PURPOSE Exercise improves quality of life in breast cancer survivors but little is known about the exercise beliefs of this population. In the present study, we examined the exercise beliefs of breast cancer survivors before and after participation in a randomized controlled exercise trial. METHODS Prior to randomization, 52 postmenopausal breast cancer survivors completed exercise belief measures based on the theory of planned behavior (i.e., behavioral beliefs, control beliefs, normative beliefs, attitudes, perceptions of control, and subjective norms). After the trial, participants assigned to the exercise group (n=24) again completed the exercise belief measures as well as measures of their future exercise plans. RESULTS The mean age of the sample was 59 years (SD=6), 75% were married, 44% completed university, 94% were disease stage I or II, 46% were currently using hormone therapy, and the mean months since diagnosis was 14 (SD=6). Adherence in the exercise group during the trial was 98.4%. Prior to randomization, the percentage of participants believing that a given exercise benefit was quite or extremely likely ranged from a low of 40.4% for reducing their risk of a recurrence to a high of 94.2% for improving their energy level. For control beliefs, the percentage of participants feeling quite or extremely confident that they could exercise in the face of a given barrier ranged from a low of 30.8% for a cancer recurrence to a high of 86.5% for bad weather. Postintervention analysis revealed that most expectations for exercise were achieved by the exercise program. Moreover, improvements in attitudes towards exercise and perceptions of control over exercise occurred in the exercise group. Specifically, instrumental attitudes increased from 6.5±0.4 to 6.7±0.4 (p=.016) whereas affective attitudes increased from 5.9±0.8 to 6.3±0.6 (p=.008). Similarly, perceptions of control increased from 5.8±1.2 to 6.9±0.3 (p <.001) but the perceived ease of the exercise program was unchanged (5.7±0.7 to 5.9±0.9; p=.465). Finally, all participants in the exercise group planned to continue exercise after the trial with a clear preference for variety in the type and context of exercise. CONCLUSION These findings suggest that breast cancer survivors have varied expectations for exercise that were generally met by our exercise program. The findings are discussed in terms of the veracity of exercise beliefs held by breast cancer survivors as well as the aspects of our program that may have contributed to the high adherence rate and the positive changes in exercise beliefs.