Despite the potential of online commenting spaces for public deliberation, they are often full of destructive or uncivil and aggressive comments. Based on research on social learning and social influence, we conducted an online experiment to investigate the effects of uncivil comments on readers' cognitive, emotional, and behavioral reactions. The experiment was built on a one-factorial between-subjects design including four experimental conditions and a control group: Participants were exposed to a news article and six user comments of which zero, one, three, or six were uncivil. Results suggest that exposure to uncivil comments can lead to an increase in readers' hostile cognitions. The effect, however, does not rise with exposure to a higher proportion of incivility. No significant effects were found on hostile emotions or the use of incivility in readers' own comments.