This investigation was aimed at studying the relations between executive functions (EFs) and categorical emotion understanding while controlling for preschoolers' IQ, language ability and theory of mind (ToM). Specifically, we wanted to analyse the association between emotion understanding and set shifting, due to the lack of studies with this EF. Data of 75 children aged 4½ years (52% boys) was collected in two laboratory visits. Emotion understanding was assessed using the "Emotion Recognition Questionnaire," inhibitory control using the "Head-Toes-Knees-Shoulders" task and set shifting using a version of the Dimensional Change Card Sort task. IQ was evaluated using the "WPPSI-R," language using the "Peabody Picture Vocabulary Test-Revised"; and ToM using six standardized tasks. Set shifting, but not inhibitory control, predicted emotion understanding, over and above mothers' age, and children's IQ, language ability, and ToM. Mothers' age and children's language ability were also significant predictors in the final regression model. Results suggest that the capacity to shift mental sets is linked with inter-individual differences in children's understanding of situational causes of emotion. Therefore studying EFs as correlates of emotion understanding is an important focus of future research.