The current research tests how comparisons in the moral domain differ from other social comparisons in three ways. First, an initial experience-sampling study shows that people compare downward more strongly in the moral domain than in most other domains (Study 1, N = 454), because people like to feel moral and present themselves as moral. Second, the classic threat principle of social comparison holds that people choose downward comparisons to improve their well-being after a threat to their self-esteem. We propose that in the moral domain the threat principle is intensified because morality is a uniquely important and central comparison domain. Across seven experiments (Experiments 2a and 2b, 3a–3c, 4a and 4b), we find that people search for downward comparisons much more than in other domains. This effect is so strong that people are willing to forgo money and incur time costs to avoid upward moral comparisons when threatened. Third, another classic principle of social comparison holds that people only consider comparisons that are diagnostic (i.e., close or similar) and therefore self-relevant, while dismissing extreme or dissimilar comparisons as irrelevant. We propose that this diagnosticity principle is attenuated because morality is a binding code that applies equally to all humans. Across four experiments (Experiments 5a and 5b, 6a and 6b), we find that even the most extreme and dissimilar moral (but not other) comparisons are deemed relevant and potentially threatening. Together, these twelve studies (total N = 5,543) demonstrate how moral comparisons are a ubiquitous but fundamentally distinct form of social comparison with altered basic principles.