DescriptionDespite the potential of online spaces for the democratic development of public discourse, concerns over aggressive and uncivil interactions in those spaces are rising. Online incivility is the term to define the features of a discussion that convey an unnecessarily disrespectful tone toward the participants or the topic. Concerning the adverse impact of online incivility on users, we sought to explore ways to reduce online incivility to promote secure and trustworthy online debate culture. Meanwhile, the web is becoming increasingly multimodal, and images are known to be effective in improving emotions. The broaden-and-build theory of positive emotions suggested that generated positive emotions may impact incivility levels. To help reduce online incivility, we conducted a one factorial between-subject online experiment with three conditions (N = 105). We compared the three background images (positive, neutral, and baseline) embedded in online discussion forums to identify an efficient way of reducing online incivility. The data gathered from surveys and participants’ online comments were qualitatively and quantitatively analyzed to answer the research questions. The results showed that not only positive background images but also neutral background images may be effective in reducing online incivility. Given that the neutral background image was less likely to be recognized by the participants in this study, embedding neutral background images could be an unobtrusive yet effective strategy to reduce uncivil conversations on online discussion forums. The results will pave way for designing more civil discussion platforms in online settings.