This study explores the effects of intergroup vicarious ostracism on individual prejudicial attributions and aggressive intentions. It takes Tibetan and Hui college students in northwestern China as participants. Study 1 and Study 2 explore the difference in observers' prejudicial attributions and aggressive intentions, respectively, when the group members who experienced ostracism (Tibetan college students) observed an in-group member being ostracized by out-group members versus an in-group member being ostracized by in-group members. Results show that those in-group participants, i.e., the Tibetan college students, who observed an in-group member being ostracized by out-group members, showed much higher prejudicial attributions, F(1, 106) = 19.65, p < .001, ηp2 = .156, and aggressive intentions, F(1, 108) = 10.51, p = .002, ηp2 = .089, toward ostracizers than those who observed an in-group member being ostracized by in-group members. In Study 3, Hui college students were recruited as participants to further test the results of Study 1 and Study 2. In addition, we also found that under the out-group conditions, prejudicial attribution mediates the effects of inclusionary status on aggressive intentions (95% bias-corrected confidence interval did not include zero; 95% CI [0.15, 0.69]). This study shows that ostracizers’ group membership could affect observers' prejudicial attributions and their aggressive intentions toward the ostracizers.