Groups involved in ongoing genocidal conflicts may appeal to third parties, who are neither perpetrators nor victims, as potential allies. Three studies investigated social psychological factors that influence citizens of a third party country to support interventions in a genocide. Study 1 (n=135) examined the impact of social categorization on endorsement of prosocial actions, and the mediating role of psychological antecedents (e.g., perception of complicity in the genocide due to inaction, perception that the ingroup could be held accountable for their inaction, and guilt for the situation of the victims and for the ingroup’s inaction). Framing the genocide in terms of the victimization of particular individuals appears to be more effective in eliciting appraisals and emotions that encourage support for intervention. Study 2 (n=100) built on the results of Study 1 to explore whether the impact of recategorization of the victims as humans (versus outgroup members) on prosocial actions and its antecedents was moderated by individuals’ evaluation of human beings (humanity-esteem). The moderation hypothesis was not supported; yet, portraying the victims as a part of a common humanity was linked to greater feelings of guilt for the victims’ plight. In addition, the more people held humans in high esteem, the more likely they were to endorse government intervention. Study 3 (n=321) assessed whether the relations among complicity, feelings of guilt and prosocial actions were altered when competing behavioral norms were made salient (i.e., the norm of a responsibility to protect versus the norm of non-intervention in a sovereign country). It appears that people were more likely to comply with norms that prescribed demanding actions (e.g., the protection of others) when there were no alternative norms that provided an escape from such obligations. The implications of these findings for citizen support for international interventions in genocidal conflicts are discussed.