Relational aggresion is a subtle form of aggressive behaviour that uses dyadic relationships and manipulation as a vehicle of harm. Little is known about relational aggression in preschool-age children in cultural contexts outside the United States. This study examined relationally aggressive behaviours and prosocial behaviours in Australian preschoolers. The sample consisted of 60 children aged from three to five years (35 boys, 25 girls). Teachers rated children's social behaviour in terms of relational aggression and prosocial behaviour. Results indicated that teachers report significantly more relational aggression in the oldest age group of children (aged > 4.5 years). Relational aggression was related to lower scores of prosocial behaviour (p < 0.05). No significant differences were found between boys' and girls' engagement in relational aggression and prosocial behaviours. Results are discussed in terms of the importance of recognising the prevalence of these aggressive behaviours in Australian preschool-age children and the need for immediate intervention.