The goal of this study was to examine the relationship between the quality of classroom interactions in kindergarten and executive functions (EFs) among 5-year-old children. The sample consisted of 118 children, with a mean age of 73.34 months (SD = 4.22), from 12 kindergarten classes. The quality of classroom interactions was measured using the Classroom Assessment Scoring System (CLASS), while the children's EFs (working memory (WM), inhibition, cognitive flexibility, and planning) were measured using various tests conducted on the children (e.g. Forward and Backward Digit Span). The results show that emotional support in the classroom was positively correlated with EF skills among the children, in particular, those related to WM and cognitive inhibition. Moreover, the results indicate that instructional support was negatively correlated with the children's WM. Further analyses demonstrated that gross family income reduced the association between instructional support and WM. These findings attest to the importance of emotional support for the development of EFs, particularly WM, and bring out the potential moderating effect of family characteristics (e.g. gross family income) on executive functioning.