The purpose of this research was to examine how non-Aboriginal Canadians might respond if the label genocide is used to describe the historical mistreatment of the Aboriginal Peoples’ of Canada. In two studies, I manipulated the perception of Residential Schools as genocide by informing (or not informing) undergraduate student participants that some people believe what happened should be labeled genocide. I also assessed the potential moderating role of knowledge by either measuring participants’ pre-existing knowledge of Residential Schools or manipulating how much participants learned about Residential Schools through a passage. Overall, participants’ reactions to the label depended on what they knew about Residential Schools such that participants with a superficial level of knowledge responded defensively to a description of Residential Schools as genocide, while participants with no knowledge or high levels of knowledge responded positively. Findings provide theoretical insight into how knowledge affects perpetrator group members’ reactions to historical harms.