The present study investigated the interplay between children's mathematical skills and their mothers' and fathers' engagement in numeracy activities. One hundred and five Hong Kong Chinese children and their fathers and mothers were assessed at two time points, first in their second year of preschool, then one year later in their third year. At both time points, all of the fathers and mothers independently reported how frequently they engaged in numeracy activities with children, and all of the children were tested individually to evaluate their symbolic and non-symbolic mathematical skills. The results showed that mothers' application activities positively predicted children's later non-symbolic mathematical skills. Children's non-symbolic mathematical skills negatively predicted their mothers' later number skill activities, and their symbolic mathematical skills negatively predicted their fathers' later number skill activities. Finally, mothers' number book activities positively predicted fathers' later number book activities, and mothers' number skill activities positively predicted fathers' later number skill activities. These findings highlight the importance of mothers' application activities to children's number learning and the potential role of children's weak mathematical skills in eliciting parental engagement in number skill activities. They also underscore the positive effect of mothers' engagement in numeracy activities on fathers' engagement.