Future trainees go through difficult decision-making processes when starting their first psychotherapy training. The choice of training in psychotherapy integration is a specific type of this process. In this study, qualitative data were obtained from the motivational letters, in-depth semi-structured interviews and e-mail questionnaires of 26 future trainees to answer the research question, "How do trainees choose their first psychotherapy training?" We primarily employed the grounded theory approach as well as consensual qualitative research to shed light on the central category of "Gaining Certainty" to enter the training. This category was elaborated into a four-phase model, specifically comprised of the: (1) "Critical Comparison", (2) "Identification", (3) "Self-Confirmation" and (4) "Waiting" phases. The model was then discussed in connection with relevant concepts, such as the degree of complexity and flexibility within the epistemological development of trainees [Vasco, A. B., & Dryden, W. (1994). The development of psychotherapists' theoretical orientation and clinical practice. "British Journal of Guidance & Counselling", 22(3), 327-341].