Psychological counseling skills are the most important part of the psychological counselingprofession. Psychological counseling candidates have the opportunity of performing theseprofessional skills previously learned theoretically within the practice course of psychologicalcounseling with another person during their undergraduate education and they receivesupervision support for these practices. This study presents mixed-pattern research examiningthe effect of group supervision on the psychological counseling self-efficacy of psychologicalcounselor candidates. Quantitative data were obtained from Counselor Activity Self-EfficacyScale and qualitative data was obtained from the evaluation reports of the psychologicalcounselor candidates. The quantitative findings show that group supervision is effective on allthe subscales (exploration, insight, action, conflicts in relationships and client problems) ofpsychological counseling self-efficacy. The qualitative results backing up these findings provethat the responses of the participants can be divided into four categories of emotions,professional development, boosters, and difficulties. As a result, the findings of this researchshowed that the group supervision carried out in the individual psychological counseling coursepositively affected the psychological counseling self-efficacy perceptions of the psychologicalcounselor candidates. Based on these findings, it has been suggested to take into considerationthe improvement of the self-efficacy levels of psychological counselor candidates as well as theacquision of professional skills in counselor education.