This study explored participant roles in aggressive behavior among 95 children aged five to seven years, in a collectivistic culture, South Korea. Using a short‐term longitudinal design, three types of nomination (peer, self, and teacher) were obtained for four participant roles (aggressor, victim, defender‐stop, and defender‐tell) and for four types of aggression (physical, verbal, social exclusion and rumor spreading). Assessments were made of stability of participant roles over time; inter‐rater concordance among informants; discriminability; and relationships with sex, and likeability. Children tended to report themselves as victim and their peers as aggressors, especially for social exclusion. Nominations for aggressor showed highest stability over time and inter‐rater concordance. Social exclusion showed different characteristics from other types of aggressive behavior in terms of its frequency and inter‐rater concordance of role nominations. The type of defender (defender‐stop or defender‐tell) had different correlates with likeability. Findings are discussed in relation to different perspectives on social exclusion, and the defender role. Some different findings related specifically to social exclusion may be related to the particular nature of aggression or wang‐ta in South Korea. Aggr. Behav. 42:287–298, 2016. © 2015 Wiley Periodicals, Inc.