This study aims to investigate the effects of a home connection program in promoting parental mathematical interaction, teacher-parent cooperative relationship, and 3-year-olds’ mathematical ability. Forty-two 3-year-olds and their parents, from two childcare centers, were sampled; 21 children from one center served as the experimental group, and 21 children from the other center served as the comparison group. In order to investigate significant differences between the two groups, independent and paired t-tests were carried out after 26 sessions of the home connection program over 9 weeks applied to the experimental group. As a result, the home connection program was shown to contribute to the enhancement of parents’ mathematical interaction, parent-teacher cooperative relationship, and 3-year-olds’ mathematical ability. This study can make an important contribution to further research on the development of more practical home connection programs for improving a developmentally appropriate home environment to aid children’s mathematics learning.