The present study aims to examine kindergarten children's performance regarding the part-whole relations and the strategies they use. The qualitative case study method was used to gain an in-depth understanding of the researched subject. Participants in the study were 43 children (21 girls and 22 boys) attending the kindergarten in six public schools run by the Ministry of National Education (MoNE). The age of the participants varied between 61 and 80 months. In order to determine children’s performance regarding the part-whole relations of numbers, interviews were held with each of them for 20 minutes. Because of the pandemic, the interviews were conducted online, using the Zoom application, in the spring semester of the Academic Year 2020-2021. Interview questions prepared in the form of individual PowerPoint slides, with different visuals on each slide, were presented to the children by the researcher in the form of a game. Children were asked 3 types (finger patterns, visual forms, hidden objects) of tasks including part-whole relations of numbers ranging from 1-7. Findings indicated that about half of the children were able to give correct answers in the tasks presented to them. Further, the types of tasks used to present the number representing the whole also did matter. One of the most interesting findings of the present study was that children who used the strategy of part-whole relations performed better compared to those who used the counting strategy. As a result, it is recommended preschool teachers, and also curriculum developers enrich the teaching process with activities that encourage thinking about numbers in terms of their parts.