Background The Self-Expression Emotion Regulation in Art Therapy Scale (SERATS) was developed as art therapy lacked outcome measures that could be used to monitor the specific effects of art therapy. Although the SERATS showed good psychometric properties in earlier studies, it lacked convergent validity and thus construct validity. Method To test the convergent validity of the SERATS correlation was examined with the EES (Emotional Expressivity Scale), Emotion Regulation Strategies for Artistic Creative Activities Scale (ERS-ACA) and Healthy-Unhealthy Music Scale (HUMS). Patients diagnosed with a Personality Disorder, and thus having self-regulation and emotion regulation problems (n = 179) and a healthy student population (n = 53) completed the questionnaires (N = 232). Results The SERATS showed a high reliability and convergent validity in relation to the ERS-ACA approach strategies and self-development strategies in both patients and students and the HUMS healthy scale, in patients. Hence, what the SERATS measures is highly associated with emotion regulation strategies like acceptance, reappraisal, discharge and problem solving and with improving a sense of self including self-identity, increased self-esteem and improved agency as well as the healthy side of art making. Respondents rated the SERATS as relatively easy to complete compared to the other questionnaires. Conclusion The SERATS is a valid, useful and user-friendly tool for monitoring the effect of art therapy that is indicative of making art in a healthy way that serves positive emotion regulation and self-development.