Teachers' emotions in the classroom shape their ability to nurture positive relationships with young children. There is increasing interest in understanding how teachers manage and express their emotions on the job through the use of emotional labour, or the deliberate expression or suppression of emotions to achieve organizational goals. This study investigates how preschool teachers' emotional labour informs their interactions with young children. Using quantitative survey and observation data from 123 preschool teachers, we found that preschool teachers' use of emotional labour, particularly surface and deep acting, and their limited perceptions of emotional display rules were linked to the quality of their interactions with young children. Also, the associations between emotional labour and teacher-child interactions were moderated by their perceptions of emotional display rules. Findings have implications for early childhood care and education policy and practice, as well as future research related to the emotional aspects of preschool teachers' work.