The aim of this study is to contribute to the description of an effective supervision process through the medium of understanding the experiences of students and also the role and impact of these experiences on the development of them as counselors regarding individual counseling practicum supervision conducted across different levels of counselor education. Besides, it is examined the differences in supervision regarding experiences across levels of counselor education. The research group consisted of totally 34 students including 8 doctorates, 7 master and 19 undergraduate students who voluntarily participated in the study. The Critical Incidents Technique, as a type of qualitative design, was used in the study. The research data was collected by Critical Incidents Form developed by the researcher and analyzed by content analysis. The five themes emerged regarding the most influential and the most important critical incidents during supervision and included supervisor feedback, supervisor characteristics, peer feedback and behaviors, supervision techniques and vicarious learning. Moreover, the six themes emerged regarding the impact of critical incidents on the development of students and included managing sessions; professional confidence; professional knowledge, skill and awareness; self-awareness; emotional experience and supervision. The results also showed that there were some differences regarding critical incidents and their impact across education levels. The results are discussed and interpreted in light of the literature. Besides, some suggestions are provided to counselor educators and researchers.