The objective of this study is to explore the effect of the Big Math for Little Kids Program (BMKL) on the mathematical development of bilingual preschool children. For this purpose, an experimental design with pre-test/post-test with control group was employed. A total of 60 children from Diyarbakir were included in the research sample. Of these, 30 were assigned to the experimental group and 30 to the control group. In the study pretest-posttest with control group experimental model was used. The data of the study were collected through the Tests of Early Language Development Test (TELD-3) to determine children with adequate language skills of their own age group, and Test of Early Mathematical Ability (TEMA-3) to assess early mathematical development of children. BMLK program were applied to the experimental group for 12 weeks by the researcher. The main themes of the four units are numbers, shapes, patterns and measurement skills. After the experiment, TEMA-3 test and TELD test were applied to the experimental and control groups as post-test. The obtained data were analyzed by using Mann-Whitney U and Wilcoxon tests. As a result of the study, it was identified that the Big Math for Little Kids Program has a statistically significant effect on early mathematical skills of children in favor of the experimental group when compared to the control group.