The present study was designed to examine mothers' emotional reactions, causal attributions, and socialization strategies in response to preschool children's engagement in proactive and reactive physical aggression with peers during free play at school. Participants were 84 mothers (M-age=31.83, SD=4.48) with preschool-aged children (M-age=4.92, SD=0. 97), residing in Ankara, Turkey. Supporting our expectations, mothers reacted with negative emotions to both functions of aggressive behaviours, with less anxiety, disappointment, embarrassment, and guilt for reactive aggression. They also believed that reactive aggression is more contextually dependent and intentional and reported more indirect (e.g., asking the child, teacher, or other children to find out more about the situation and aggressive episode) and other-oriented strategies (e.g., telling the other child to behave properly) to address these behaviours. Overall, our findings suggest that Turkish mothers' feelings, perceptions, and socialization approaches to childhood aggression vary depending on the functions of aggression, and mothers perceive preschool-aged children's engagement in reactive aggression in the school setting as relatively more acceptable than proactive aggression. Copyright (c) 2016 John Wiley & Sons, Ltd.