Background: Clinical psychologist education in Taiwan adopts competency-based approach. In this training framework, there are six core competencies, including: (a) academic knowledge, (b) befriending, (c) clinical practice, (d) drug-related systems, (e) empathy and ethics, and (f) functional development. The goal of this two-stage study was to extend these six core competencies and establish the sub-competencies of Taiwan's clinical psychologists' training and education. Methods: In this two-stage study, the first stage involved verifying the content validity of the sub-competencies, and the second stage involved evaluating the importance of those competencies by using the Fuzzy Delphi method. In stage 1, to ensure content validity, 1-hour in-depth individual interviews were conducted with three psychologists and expert groups when determining the sub-competencies. In the stage 2, a total of 25 clinical psychologists (12 female and 13 male) completed the Fuzzy Delphi questionnaire. Results: Based on the six-core-competency framework, 18 sub-competencies were established in collaboration with three clinical psychologists and the Teaching and Training Committee of the Taiwan Association of Clinical Psychologists. The Fuzzy Delphi analysis revealed that the importance indices of the 18 sub-competencies were all higher than 7. Psychopathology, psychological assessment, psychotherapy, case formulation, and client-centered attitude were the major competencies, each with an importance index as 9. Conclusions: Based on the six-core-competency framework, 18 sub-competencies were established for clinical psychologists and the 5 most important sub-competencies could be used as the topic for continue education courses.