The objective of the present study was to investigate prosocial behaviour, aggression types and moral and social rule knowledge perceptions of 4-5 year old preschool children. The study sample included 310 children (154 female and 156 male), who were attending a pre-school education institution during the 2017-2018 academic year. A personal information form, Pre-School Social Behavior Scale-Teacher Form and Moral and Social Rule Knowledge Perception Scale were used as data collection instruments. The data were analysed with descriptive analysis, Pearson product-moment correlation coefficient and stepwise regression analysis. In the study, it was determined that there were moderate significant correlations between prosocial behaviour, aggression types and moral and social rule knowledge perceptions of 4-5 year old preschool children. It was also determined that prosocial behaviour and aggression types scores of the children significantly predicted their moral and social rule knowledge perception scores.