The authors present the development and statistical analysis, conducted under the auspices of the German Transactional Analysis Association (DGTA), of an online evaluation system of transactional analysis training.  The understanding of evaluation research is clarified, and the data-entry form and its grounding in the theory of transactional analysis are presented. Emphasis is placed on the development of the competence concept, the definition of competence categories, and the representation of the foundations of a transactional-analytic educational theory.  The scientific examination of the validity and reliability of the scales, the research process with pre-test and re-test, and the evaluation of the data in the system of online evaluation are extensively documented.  In conclusion, it is claimed that this online-based DGTA evaluation is one of the few result-oriented teaching evaluation instruments in the German-speaking countries which meets scientific control criteria and is published. Citation - APA format: Nagel, N., König, J., Ottmann, S., & Hahnle, A. (2017). The development by the German Transactional Analysis Association of a scientifically-based online evaluation system of transactional analysis training. International Journal of Transactional Analysis Research & Practice, 8(2), 3-23.