Many traditional accounts of moral development posit that children actively construct moral beliefs by reasoning about the distress they directly perceive in the aftermath of harmful or unjust actions. However, these accounts cannot straightforwardly explain the development of moral beliefs about harmless but tabooed actions. For cases such as these, when no negative behavioral consequences are apparent, top-down socialization processes (e.g., verbal instruction or "testimony" from adults) may instead influence moral development, as well as emotional reactions such as disgust. The present research consists of four studies that empirically examine the mechanisms leading to the formation of moral values involving victimless actions. Seven-year-old children were recruited as participants in this research. They were shown pictures of anthropomorphic aliens engaged in novel body-focused or environment-focused actions, all of which were harmless. After being exposed to one of various experimental manipulations, children were asked to judge whether the depicted actions were "wrong" or "OK". It was hypothesized that participants would readily acquire new moral beliefs upon being exposed to each of the experimental manipulations that were employed, even though none invoked suffering or harm. Study 1 (N = 64) found that information about unnaturalness and the invocation of disgust each elevated moralization, and that their independent effects were compounded when these manipulations were presented jointly. Study 2 (N = 90) demonstrated that verbally presented testimony about disgust, but not the induced emotional experience of disgust, was an effective mechanism for moralization, particularly for children who were more disgust sensitive. Study 3 (N = 30) found that children responded to testimony about anger with similar patterns of moralization as when given testimony about disgust, but that anger-based testimony was especially effective for children who were more highly prone to anger. Study 4 (N = 28) found that children's moral beliefs were retained after a prolonged time delay. In sum, across four studies, children were found to rapidly form new moral beliefs about victimless actions, particularly upon exposure to emotionally laden testimony. Overall, this research demonstrates that children are susceptible to swiftly acquiring moral beliefs even in the absence of obvious adverse outcomes.