In this study, it was aimed to reveal the mathematical games designed by secondary school preservice mathematics teachers and their views on this process. The participants of the study, in which a case study, one of the qualitative research designs, was used, consisted of 45 pre-service secondary school mathematics teachers who took the Teaching Mathematics with Games course. The data obtained from the study were subjected to descriptive and content analysis. According to the results obtained from the study, while the majority of the games were designed as board/card games, the most preferred learning area was numbers and operations. In addition, according to the grade levels, the most games were designed for the 8th grade and the least for the 5th grade level. In the process of mathematical game design, pre-service teachers mostly aim to provide meaningful learning, develop procedural skills, reinforce what has been learned, and make learning mathematics fun. In addition, although the pre-service teachers experienced some difficulties during the game design process, it was determined that this process affected them positively in cognitive, affective, and pedagogical terms.