This study aims to determine the opinions of principals and teachers about the inspection of classrooms conducted by school principals. The phenomenological method, which belongs to the qualitative methods, was used for the research. The study's research group consisted of 10 school principals, selected according to the criterion sampling, working in independent secondary schools in the center of Bolu during the second semester of the 2021-2022 school year, and 20 teachers working in these schools. The research data were collected using semistructured interview forms developed by the researcher, and the data were analyzed using descriptive analysis and content analysis. The research found that principals and teachers were positive and negative about principals' knowledge and skills in inspecting classrooms. Principals' problems in classroom observation, the appropriateness of principals' classroom observation, and the effects of principals' classroom observation on teachers' development were also revealed. In addition, it was found that both principals and teachers frequently mentioned: "the topic of in-service training" for principals to make principal inspections more effective. It was also found that the influence and authority of principals should be strengthened, and teachers expressed strong opinions about increasing inspection time. In connection with these findings, it was suggested that principals receive in-service inspection training, extend inspection duration, conduct inspection according to objective criteria, and expand principals' authority for instructional inspection.