Relationships among full constructs of the transtheoretical model using a sample of 121 adults with mild intellectual disabilities in Taiwan were examined. Self-reports of stages of change and transtheoretical model psychosocial measures were gathered through interviews. Although MANCOVA revealed that behavioral processes of change, cognitive processes of change, self-efficacy, and perceived pros increased across stages, we did not find a clear linear pattern of association. Direct discriminant function analysis indicated that the most important predictors of stages of change were behavioral processes, cognitive processes, and self-efficacy. The overall stage of change classification accuracy using transtheoretical model psychosocial constructs was 56.2%. Psychosocial measures specifically developed for this population should be further explored.