Social movements often use protests and other collective actions to draw public attention to their cause, yet the psychological reactions to such actions from their targeted audience is not well understood. This research investigates uninvolved bystanders’ immediate responses to collective action using a quasi-experimental field study designed around a racial justice protest that took place at a large public university in the United States. We surveyed two student samples exactly one week apart at the same time and location, first in the absence of protest and then again at the time of a racial justice protest (Total N = 240). We found that participants who believed that racism was not a problem on campus had more negative attitudes toward racial justice protests and protesters, as well as lower support for anti-racist efforts on campus on the day of the protest, compared to the day without a protest. These findings provide initial evidence that a protest encounter may trigger a backlash effect amongst those who have the most resistant attitudes toward social change. Background Racial justice movements often have a strong presence on college campuses. Since the Black Lives Matter movement emerged in 2013, a series of protests have occurred in universities across the United States to push for fair treatment of racial minorities. Why was this study done? Protests typically aim to gain the attention of broader society and mobilize greater support for their cause. We can observe this from the range of tactics and contentious actions that protesters typically undertake to disrupt everyday life. Thus, being confronted by a protest might trigger backlash among some people. We therefore aimed to understand how people react when they directly encountered a protest in their social environment. What did the researchers do and find? We surveyed members of a campus community exactly a week before, and during a racial justice protest that occurred at a U.S. university. The research distributed brief anonymous surveys to participants who happened to be at the location of the protest. We found that among people who had relatively weaker perceptions of campus racism, they reported more negative attitudes toward racial justice protests and protesters, as well as less support for anti-racist efforts on campus when they physically encountered a racial justice protest (compared to when they did not encounter a protest). What do these findings mean? Although protests are a means toward social and political change, it might trigger immediate backlash among people who do not perceive a strong sense of injustice. By focusing on the attitudes of people who encounter a protest, this study contributes to our understanding of how protests can influence the attitudes of broader society.