Gaining insight is considered a cornerstone of psychodynamic psychotherapy. Existing tools used to measure insight mainly include patients' self-report questionnaires and external coding of therapy sessions. To expand on the available tools, the present study developed a comprehensive coding system for the Self-Understanding of Interpersonal Patterns Scales-Interview (SUIP-I; Gibbons & Crits-Christoph, 2017). A total of 55 patients enrolled in a randomized controlled trial received psychodynamic psychotherapy for depression and were interviewed using the SUIP-I at baseline. A comprehensive coding system was developed for rating the interviews, based on a Likert scale for each of the six levels of insight. The content validity, psychometric properties, and the reliability and validity of the coding system were examined. The new SUIP-I coding system demonstrated interrater reliability in the "excellent" range, ICC (1, 1) = .91-.97, for all the six levels, and adequate internal consistency (Cronbach's α = .81). Support for convergent validity was gained, as manifested in a significant positive association of the SUIP-I with alliance expectation and affiliation, and a significant negative association with avoidance attachment. Support for discriminant validity was also gained, as manifested in a weak, nonsignificant association between the SUIP-I and self-esteem. The proposed comprehensive coding system shows good initial reliability and validity. Research is needed to further establish the psychometric properties of the new SUIP-I coding system. Clinical Impact Statement Question: Can a coding system be developed, based on a Likert-scale, for the Self-Understanding of Interpersonal Patterns Scales-Interview such that it can represent a systematic assessment of insight? Findings: The developed Likert-scale-based systematic coding system can be used by clinicians to evaluate the level of insight. Meaning: Insight can be reliably quantified as a continuous range based on a semistructured interview. Next Steps: After further validation of the SUIP-I coding system, it can be used to create an understanding of differences in level of insight between individuals, as well as changes within individuals throughout treatment.