Intergroup conflict often reduces prosocial behavior toward out-group members, yet little is known about how the medium of interaction influences this tendency. The present research investigated whether prosocial behavior toward political out-group members differs between online and face-to-face contexts. Two studies were conducted using the Dictator Game as a behavioral measure of prosocial resource allocation. In Study 1, 212 participants were randomly assigned to interact with either an in-group or out-group member in a text-based online environment in which group membership was established through political attitude. Participants in the in-group condition exhibited significantly higher prosocial behavior (M = 0.79, SD = 0.35) than those in the out-group condition (M = 0.60, SD = 0.45), indicating a robust intergroup bias. In Study 2, 31 participants completed a laboratory-based Dictator Game after a face-to-face encounter with a counterpart who was presented as either an in-group or out-group member. Although participants showed a numerically higher rate of prosocial behavior toward in-group members (M = 0.73, SD = 0.29) than out-group members (M = 0.60, SD = 0.32), this difference was not statistically significant. These findings suggest that intergroup bias in prosocial decision-making may be amplified in text-based online environments but attenuated during face-to-face encounters. The results support theoretical accounts emphasizing the role of individuation and social cues in reducing reliance on categorical group distinctions and promoting more equitable treatment of out-group members.