--- - |2 Abstract When witnessing an uncivil, immoral, or discriminatory behavior, bystanders have the opportunity to “speak up” and confront the perpetrator about his/her act. We examined whether the closeness of the relationship between the bystander and the perpetrator affects the bystander's reaction. We asked middle schoolers, high schoolers, and university students (N = 1,386) to indicate how they would react if they were to witness each of 26 uncivil, immoral, or discriminatory behaviors. We experimentally manipulated the relationship to the perpetrator, who was described as a friend, an acquaintance, or a stranger. Results showed that the closer the relationship to the perpetrator the greater the bystander's self‐reported likelihood of “speaking up.” The findings speak to the role of close relationships in the perpetuation of social norms. They also suggest ways to curb anti‐social behaviors in a variety of school and organizational settings. - European Journal of Social Psychology, EarlyView.