This study adopted a multidimensional approach to investigate the relationships between children’s executive function, emotion understanding and forms and functions of aggression in children from five different preschools in Christchurch, New Zealand. The study aimed to explore potential gender differences within these relationships and to see which components of executive function and emotion understanding would be most predictive of different subtypes of aggression. Potential interactions between executive function and emotion understanding were also explored as predictors of aggression. One hundred and thirty-seven preschool-age children (61 boys and 77 girls) from 2 to 5 years of age (mean age = 3.9, SD = 0.73) completed inhibitory control and cognitive flexibility tasks and expressive and receptive emotion understanding tasks. Teachers completed questionnaires on children’s aggressive behaviours. Emotion understanding emerged as a significant predictor across aggression forms and functions. Distinct patterns were observed with lower receptive emotion understanding associated with reactive aggression and higher levels linked to proactive aggression. Lower receptive emotion understanding and higher inhibitory control predicted increased teacher- reported reactive relational aggression. This suggests there is a more intricate relationship between executive function, emotion understanding and aggression in preschool-age children that extends beyond a simple deficit-based explanation.