Purpose: The aim of this study was to investigate the perceptions of undergraduate counseling trainees in regards to the use of the structured peer group supervision format and its effect on their counseling self-efficacy beliefs. Method: This study utilized a mixed method research design incorporating both qualitative and quantitative methodologies. To obtain the opinions of counseling trainees in regards to the use of the structured peer group supervision format, qualitative data was collected via a demographic information form and survey developed specifically for this research. While, the quantitative data for the study was collected via a Counselor Activity Self-Efficacy Scale (CASES) utilized to measure the counseling self-efficacy levels of the participating counseling trainees. The research participant group was comprised of senior-level university students studying in the Counseling and Guidance program at a state university located in Ankara, Turkey. The participant group for the qualitative portion of the study included 16 undergraduate-level counseling trainees, while the participant group for the quantitative portion included 21 undergraduate-level counseling trainees. Findings: The qualitative findings indicated that the trainees' perceptions were clustered into four main themes: (1) contributions of the model, (2) strengths of the model compared to individual supervision, (3) aspects of the model that need improvement, and (4) applicability of the model for undergraduate-level counseling students. The quantitative findings revealed that the structured peer group supervision process positively affected the growth of the trainees' counseling self-efficacy beliefs. Implications for Research and Practice: The results suggested that the structured peer group supervision format could be a useful and practical means of providing appropriate and effective supervision for undergraduate-level counseling trainees in Turkey.