This study aimed to examine whether the expectation for physical activity to minimize dementia risk was associated with physical activity level and whether this association was moderated by perceived high value of dementia prevention among older adults. Participants (n = 2,824) completed questionnaires and wore accelerometers to measure their average daily steps and levels of physical activity. The expectation for physical activity to minimize dementia risk, perceived value of dementia prevention, and potential covariates (expectation of other desirable outcomes, demographics, and health-related factors) were also measured. The main effects of the expectation and perceived value and their interaction were not significant for physical activity variables in generalized linear models. These findings indicate that expecting physical activity in minimizing dementia risk might not be sufficient to influence physical activity behavior regardless of perceived high value of dementia prevention among older adults.