Lack of reliable and valid measures of therapist competence is a barrier to dissemination and implementation of psychological treatments in global mental health. We developed the ENhancing Assessment of Common Therapeutic factors (ENACT) rating scale for training and supervision across settings varied by culture and access to mental health resources. We employed a four-step process in Nepal: (1) Item generation: We extracted 1081 items (grouped into 104 domains) from 56 existing tools; role-plays with Nepali therapists generated 11 additional domains. (2) Item relevance: From the 115 domains, Nepali therapists selected 49 domains of therapeutic importance and high comprehensibility. (3) Item utility: We piloted the ENACT scale through rating role-play videotapes, patient session transcripts, and live observations of primary care workers in trainings for psychological treatments and the Mental Health Gap Action Programme (mhGAP). (4) Inter-rater reliability was acceptable for experts (intraclass correlation coefficient, ICC(2,7) = 0.88 (95% confidence interval (CI) 0.81-0.93), N = 7) and non-specialists (ICC(1,3) = 0.67 (95% CI 0.60-0.73), N = 34). In sum, the ENACT scale is an 18-item assessment for common factors in psychological treatments, including task-sharing initiatives with non-specialists across cultural settings. Further research is needed to evaluate applications for therapy quality and association with patient outcomes.