Using a large random representative sample of Canadian employees (N = 19, 609), we examine the differential effects of three types of mistreatment from supervisors, colleagues, and customers on employees’ work attitudes and life satisfaction. The results suggest that even after controlling for the frequency of abuse, mistreatment from supervisors have a stronger negative effect on employees than mistreatment from colleagues and customers. These findings suggest that source of mistreatment is an important contextual factor to consider in examining employee reactions to workplace aggression.