Peer play provides ample opportunities for the use and development of self-regulatory and mathematical skills. This study aimed at examining whether children's engagement in solitary low-level play, interactive play and competent play influences their self-regulatory and number sense skills. The effect of demographic variables and children's social skills on these skills was also investigated. The participants in this study were 149 children (Mean age = 68 months, SD = 3.71) from public and semi-independent kindergarten programs in a city in southwest Turkey. Children's play was observed during free play time, and their self-regulation and mathematical skills were measured. Teachers rated children's social skills. Binary logistic regression was used as an analytical tool. The results showed that children's engagement in peer play significantly improved their chances of having higher number sense and self-regulatory skills. In particular, interactive play significantly contributed to children's self-regulatory and number sense skills. Moreover, child age, family income, and social skills were influential factors for these skills. The findings show the importance of peer play for supporting the development of self-regulatory and mathematical skills.