Despite the omnipresence of inter-group conflicts, little is known about the heterogeneity and stability of individuals’ social preferences toward in-group and out-group members. To identify the prevalence and stability of social preferences in inter-group conflict, we gather quota-representative, incentivized data from a lab-in-the-field study during the heated 2016 Austrian presidential election. We assess social preferences toward in-group and out-group members one week before, one week after, and three months after the election. We find considerable heterogeneity in individuals’ group-(in)dependent social preferences. Utilizing various econometric strategies, we find largely stable social preferences over the course of conflict. Yet, there is some indication of variation, particularly when the conflict becomes less salient. Variation is larger in social preferences toward in-group members and among specific preference types. We discuss the theoretical implications of our findings and outline potential avenues for future research.