Human adults incline toward moral objectivism but may approach things more relativistically if different cultures are involved. In this study, 4-, 6-, and 9-year-old children (N = 136) witnessed two parties who disagreed about moral matters: a normative judge (e.g., judging that it is wrong to do X) and an antinormative judge (e.g., judging that it is okay to do X). We assessed children’s metaethical judgment, that is, whether they judged that only one party (objectivism) or both parties (relativism) could be right. We found that 9-year-olds, but not younger children, were more likely to judge that both parties could be right when a normative ingroup judge disagreed with an antinormative extraterrestrial judge (with different preferences and background) than when the antinormative judge was another ingroup individual. This effect was not found in a comparison case where parties disagreed about the possibility of different physical laws. These findings suggest that although young children often exhibit moral objectivism, by early school age they begin to temper their objectivism with culturally relative metaethical judgments.