External supervision appeared driven by evaluation requirements of PBF with the potential to both improve and damage motivation of providers. The risk of harm calls for careful attention to factors that influence the supervisory relationship. The available forms of power should be recognised by supervisors, and used with caution. Rewards, which in their absence may be experienced as punishment, is a power form inherent to PBF in Rwanda, shaping the supervisory relationship. Promotive power sources that account for experienced and actual needs of providers appear decisive for desirable supervision outcomes.