Objectives The last two decades has witnessed a strong endorsement of competency‐based models for both practitioner training and professional supervision. The valid and reliable measurement of supervisee and supervisory competence is an essential step towards progress, yet currently there are few instruments that can claim to measure the range of supervisor competencies. The current study establishes the Supervision Evaluation and Supervisory Competence (SE‐SC) scale as a new, psychometrically sound instrument. Method A total of 142 supervisees anonymously completed overall evaluations of supervision satisfaction and supervisor effectiveness and of specific supervisor competencies using the SE‐SC instrument. The specific competencies were subjected to a hierarchical cluster analyses to determine the underlying structure of supervisory competence. Results The results supported a six‐cluster solution that included (a) Openness, caring and support, (b) Supervisor's Knowledge and Expertise as Therapist, (c) Supervision Planning and Management, (d) Goal‐Directed Supervision, (e) Restorative Competencies, and (f) Insight into and Management of Therapist‐Client Dynamics and Reflective Practitioner Competencies. The results yielded excellent internal reliability, test–retest reliability, and concurrent validity for the six clusters, with high and meaningful correlations with subscales of the Supervisory Working Alliance Inventory (SWAI) and the Supervisory Styles Inventory (SSI). More importantly, the six clusters together better predicted overall scores on supervision satisfaction and effectiveness (85% of variance) than did subscales of the SWAI (56%) and the SSI (57%). Conclusion The SE‐SC demonstrates good psychometric properties and is a useful scale to measure a supervisee's evaluation of supervisory competence.