In this article, we discuss a number of challenges with the empirical study of emotion and its relation to moral judgment. We examine a case study involving the moral foreign-language effect, according to which people show an increased utilitarian response tendency in moral dilemmas when using their non-native language. One important proposed explanation for this effect is that using one’s non-native language reduces emotional arousal, and that reduced emotion is responsible for this tendency. We offer reasons to think that there (...) is insufficient evidence for accepting this explanation at present. We argue that there are three themes that constrain our current ability to draw firm empirical conclusions: 1) the frequent use of proxies or partial measures for emotions, 2) the lack of a predictive and generalizable theory of emotion and specific emotion-types, and 3) the obscurity of a baseline level of neutrality with respect to participant emotion. These lessons apply not only to research on the moral foreign-language effect, but to empirical research in moral psychology more generally. (shrink)