Background In order to adequately assess aggression in adolescence, the Peer Conflict Scale (PCS) was developed. It evaluates both forms and functions of aggression (i.e. proactive overt, proactive relational, reactive overt and reactive relational aggression). The goal of this study was to examine the validity and reliability of the Croatian version of the Peer Conflict Scale. Participants and procedure The total sample consisted of 656 high school students from the City of Zagreb (age range 16-17, 55.33% boys). Independent exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) were conducted to determine the factor structure, and the best fitting model of the PCS on a Croatian sample. Results Both results of EFA and CFA support a proposed four-factor model of the instrument. Reliabilities of the instrument’s scales were acceptable. The measurement invariance across gender was established. In order to analyse the construct validity of the PCS, relations between aggression subtypes and the theoretically meaningful variable, i.e. anxiety, were assessed. Reactive rela-tional aggression had the highest correlation with anxiety, while proactive overt aggression did not correlate significantly with anxiety. Furthermore, gender differences in aggression subtypes were assessed, and were in accordance with past research. Conclusions Our study verifies the reliability, factor structure and construct validity of PCS in a sample of Croatian adolescents. However, the results of this study suggest that the response format should be changed. Furthermore, some items did not match well with corresponding factors and the best fitting model was the one in which those items were excluded. Therefore, we suggest that two items should be replaced with new ones.