Activities, which are defined as activities that support students’ mathematical learning and increase their levels of mathematic learning, enable the individual to be active by mentally and physically engaging in an action, to establish a cause-effect relationship, and to satisfy his/her curiosity. In this respect, activities have an important effect on the attitude towards mathematics. For this reason, it was aimed to examine the math activity preparation processes of pre-school primary teachers in the current study. To this end, the study was designed in accordance with the case study design, one of the qualitative research methods. In the analysis of the collected data, content analysis was employed. As a result of the study, it was found that the pre-service teachers prepared the activities themselves, they used books and the internet during the development process, and they prepared the activities for the introduction and ending sections of the lesson. In addition, it was observed that while preparing the activity, they considered its suitability for the level of the students and for the purpose of the lesson, they did not take into account individual differences while preparing the activities, and they made use of daily life examples in the activities. The pre-service teachers stated that they had difficulties in preparing activities suitable for the level of the students and stated that they did not consider themselves adequate in preparing activities. Therefore, more emphasis should be placed on improving the skills of developing activities suitable for primary school mathematics lessons in teacher training faculties.