The COVID-19 pandemic may be one of the greatest modern societal challenges that requires widespread collective action and cooperation. While a handful of actions can help reduce pathogen transmission, one critical behavior is to self-isolate. Public health messages often use persuasive language to change attitudes and behaviors, which can evoke a wide range of negative and positive emotional responses. Here, I discuss the role that emotional responses play in compliance with public health messages leveraging threatening or prosocial persuasive language. While our research shows both types of appeals increase willingness to self-isolate, compared to the threat message, the efficacy of the prosocial message is more dependent on emotional engagement. I discuss the implications of these results for public health messaging regarding COVID-19.