Supervision is an important component of counselor development; however, limited research exists on evaluating supervision. There is also a lack of comprehensive, psychometrically strong assessments to measure supervision competencies. In this study we focused on the development of the Supervision Competencies Scale (SCS), an assessment designed to measure a supervisor's competence. There were 416 counseling supervisors, including 194 faculty members, 111 practitioners, 33 students, 22 administrators, 14 site supervisors, 32 that reported other, and 10 that did not indicate a position. We conducted an exploratory factor analysis and found a four-factor structure (Factor 1: Supervision Skills; Factor 2: Supervision Laws and Ethics; Factor 3: Supervision Modalities; Factor 4: Supervision Knowledge) with 53 items. The SCS had strong internal consistency (Total = 0.97, subscales ranged from 0.8-0.958). Educators, trainers, supervisors, and researchers may use the SCS in various capacities to promote the development of supervision competencies.