Biology, known as the science of life in its most general definition, is one of the branches of science closest to individuals due to the subjects it contains. Therefore, knowing the concepts related to biology correctly is important for the sustainability of the learning process. In this study, it was aimed to determine the conceptual perceptions and misconceptions of prospective science teachers about photosynthesis. The research using the case study was carried out in 2020-2021. The study group of the research consists of 57 pre-service science teachers studying in the first and fourth year of a state university in Turkey. The structured interview form and focus group interview form prepared by the researchers were used as data collection tools. As a result of the research, it was determined that the conceptual perceptions of the pre-service science teachers about the substances taken from the external environment in the photosynthesis process, photosynthesis products, and the importance of photosynthesis for the ecosystem were not sufficient. In addition, in the study, it was determined that pre-service science teachers had misconceptions about the definition of photosynthesis, energy source and the importance of photosynthesis for the ecosystem.