In this study, it was aimed to investigate the pedagogical content knowledge of pre-service elementary mathematics teachers'about the concept of cylinder in the subject of geometric objects in accordance with the sub-components of subject knowledge, knowledge of teaching strategy, knowledge of understanding students and measurement and evaluation knowledge. The case study method based on the qualitative approach was used in the study. In this context, while determining the participants of the study, the purposeful sampling method was taken as a basis and seven pre-service teachers were included in the study. The data of the study were collected using the semi-structured interview. The content analysis and descriptive analysis techniques were used together in the analysis of the obtained data. As a result of the analysis, it was observed that the pedagogical content knowledge of the pre-service teachers about the concept of cylinder was not at the desired level and especially the subject knowledge and measurement and evaluation knowledge were insufficient. Furthermore, it was concluded that the pre-service teachers' knowledge of understanding students was more adequate when compared to the knowledge of teaching strategies.