The study investigated interpretive understanding, moral judgments, and emotion attributions in relation to social behaviour in a sample of 59 5-year-old, 123 7-year-old, and 130 9-year-old children. Interpretive understanding was assessed by two tasks measuring children's understanding of ambiguous situations. Moral judgments and emotion attributions were measured using two moral rule transgressions. Social behaviour was assessed using teachers' ratings of aggressive and prosocial behaviour. Aggressive behaviour was positively related to interpretive understanding and negatively related to moral reasoning. Prosocial behaviour was positively associated with attribution of fear. Moral judgments and emotion attributions were related, depending on age. Interpretive understanding was unrelated to moral judgments and emotion attributions. The findings are discussed in regard to the role of interpretive understanding and moral and affective knowledge in understanding children's social behaviour.