In recent years, attention has been paid to inappropriate parenting styles, with some studies showing that these are related to children’s problem behaviors. Previous studies have pointed out the relationship between parenting style and negative automatic thoughts of mothers, but there may be factors that change such thinking in the process from cognition to behavior. Therefore, in this study, we examined the mediating effect of mindfulness on the relationship between negative automatic thoughts about parenting and parenting style. The study sample comprised 170 mothers whose children were between the ages of 0 and six years. The mothers’ mean age was 34.0, with the range being 21–47, while the children’s mean age was 2.2 years. The study was conducted online—we performed correlation analysis. Our results showed that automatic thoughts was negatively related to Observing and Nonreactivity; in addition, Observing was not significantly related to parenting style. Additionally, we performed mediation analysis. The results showed the indirect effect of Nonreactivity, which partially mediated the association between automatic thoughts and Overreaction. A limitation of this study is the possibility of the sample including mothers of children not in the age range 0–6 years because it was conducted online.