We examined the hypothesis that physical activity will have favorable effects on measures of self-efficacy for a 400-m walk and satisfaction with physical functioning in older adults 70+ years of age who have deficits in mobility. We randomized a total of 412 adults aged 70-89 years at elevated risk for mobility disability to either a physical activity or a successful aging educational control intervention for 12 months. Participants in the physical activity intervention had more favorable changes in both outcomes as a result of treatment than those in the successful aging intervention. Gender, age, and scores on a short physical performance battery did not moderate these effects. Physical activity is an effective means of intervening on self-efficacy and satisfaction with physical function in older adults with impaired lower extremity functioning. This is an important finding in light of the importance of these process variables in behavior change and quality of life.