Understanding the factors that motivate defending behaviour from an early age is crucial in informing effective intervention in bullying. However, relatively little is known about the social, emotional, and cognitive factors that predict young children's involvement in defending behaviour. This study investigated the concurrent role of social (i.e. relational and physical aggression, prosocial behaviour, positive peer interactions, and peer rejection), emotional (i.e. anger, empathy), and cognitive (i.e. social withdrawal, inhibitory control, and attention) predictors of defending behaviour in early childhood (N = 87, "M age" = 46.74 months, SD = 10.13, 56% males). Children were recruited from kindergartens located in three diverse socio-economic communities in the South Island of New Zealand. The findings of a series of hierarchical regressions showed that, after controlling for age, lower levels of social withdrawal predicted higher levels of defending behaviour. For older children (= 46.7 months), empathy was a strong predictor of defending behaviour. Defending behaviour was positively associated with age; however, no differences were found in teacher reports of boys' and girls' use of defending. Implications for early prevention, intervention, and future research directions are discussed.