Background: In Senegal, traditional supervision often focuses more on collection of service statistics than on evaluation of service quality. This approach yields limited information on quality of care and does little to improve providers' competence. In response to this challenge, Management Sciences for Health (MSH) has implemented a program of formative supervision. This multifaceted, problem-solving approach collects data on quality of care, improves technical competence, and engages the community in improving reproductive health care. Methods: This study evaluated changes in service quality and community involvement after two rounds of supervision in 45 health facilities in four districts of Senegal. We used checklists to assess quality in four areas of service delivery: infrastructure, staff and services management, record-keeping, and technical competence. We also measured community involvement in improving service quality using the completion rates of action plans. Results: The most notable improvement across regions was in infection prevention. Management of staff, services, and logistics also consistently improved across the four districts. Record-keeping skills showed variable but lower improvement by region. The completion rates of action plans suggest that communities are engaged in improving service quality in all four districts. Conclusion: Formative supervision can improve the quality of reproductive health services, especially in areas where there is on-site skill building and refresher training. This approach can also mobilize communities to participate in improving service quality.