Power dynamics between supervisors and supervisees are inherent as a result of the hierarchical structure of supervision. Failure to adequately attend to issues of power in supervision can result in ineffective or even harmful supervision. Currently, supervisors do not have an objective measure of power dynamics within the supervisory relationship or a tool that allows for ongoing measurement and discussion of power in supervision. The authors developed the Power Dynamics in Supervision Scale (PDSS) and investigated its psychometric properties with a sample of 267 supervisees. Results from the polytomous Rasch model indicated that the PDSS items (n = 16) explained 51.77% of the variance as a single factor. Item locations on the logit scale indicate supervisees perceive differing levels of power, meaning that PDSS items adequately identified differences in power perceptions among supervisees. Supervisees perceived themselves as possessing the most power on maintaining healthy boundaries with their supervisors, a willingness to feel vulnerable in supervision, and feeling empowered in supervision. They also perceived their supervisors as possessing the most power in identifying interventions to use with clients, setting goals for supervision, and providing feedback about clinical skills in supervision. Implications for supervisors and supervision research are provided in light of the findings.