Analyze whether the content of three moral messages (deontological, ethical utilitarianism, ethical virtue) and a control message differentially affect the probability of engaging in four behaviors: Washing their hands, participating in public gatherings, staying at home/avoiding social contact, and forwarding the message to inform more people. In our study, the sender of the message is a university professor. These variables are measured in terms of their behavioral intentions and others’ behavioral intentions (beliefs about others’ behavior). Randomized Controlled Trial. Our study includes the analysis of the possible moderating effect of the country of residence (Spain n = 1,122, Chile n = 1,107, and Colombia n = 1,433). The message with content referring to ethical virtue and staying at home obtains statistically significant lower scores on the probability of carrying out public health behaviors and sharing the message received. Regarding beliefs about the behavior of others, the message of ethical virtue has the same negative effect, but only on the likelihood of other people washing their hands, staying at home, and sharing the public health message. Institutional messages aimed at promoting public health behaviors are necessary in a pandemic situation. Our recommendation is to use deontological and utilitarian, or non-moral, content.