Abstract. This study examined the association between Agreeableness and children’s selection of conflict resolution tactics and their overt behaviors at school. A total of 157 second graders responded to a series of conflict resolution vignettes and were observed three times during physical education classes at school. We hypothesized that Agreeableness would be inversely related to the endorsement of power assertion tactics and to displays of problem behaviors, and positively related to the endorsement of negotiation tactics and to displays of adaptive behaviors. Consistent with hypotheses, Agreeableness was inversely related to power assertion tactics and to displays of off-task, disruptive, and verbally aggressive behaviors. There was no evidence that Agreeableness was related to more socially sophisticated responses to conflict, such as negotiation, with our sample of second grade students; however, it was related to displays of adaptive behaviors, specifically on-task behaviors. Limitations, including potential reactivity effects and the restriction of observational data collection to one school-based setting, are discussed. Future researchers are encouraged to collect data from multiple sources in more than one setting over time.