Ostracism is a common social occurrence which has severe consequences on psychological well-being. Whereas many studies have explored the perceptions and experiences of ostracized individuals, less work has explored how individuals perceive ostracism that is experienced by another person, particularly when the reason for ostracism is ambiguous. Further, research has not examined how in-group versus out-group status of the group influences a perceiver’s attributions for ostracism, and the effects of these attributions on evaluations of the group and victim. The current study explores the extent to which manipulated in-group versus out-group status relates to differential evaluations of an ostracized individual and ostracizing group, in the context of an observed episode of ostracism within an online chat room. Additionally, the extent to which these evaluative differences are due to ‘internal’ versus ‘external’ attributions for the observed ostracism are explored. This research will broaden the current understanding of perceived derogation of in-group versus out-group members, as previously studied in relation to the ‘black sheep effect’ (Marques, Yzerbyt, & Leyens, 1988). Additionally, this work will contribute to understanding related phenomena such as pro-social behavior in response to observing the ostracism of another individual.