Moral foundations theory (Graham & Haidt, 2010) has been the dominant theory of morality within social psychology for the last decade, and the Moral Foundations Questionnaire (MFQ; Graham, Nosek, Haidt, Iyer, Koleva, & Ditto, 2011) is currently the only multi-item measure to study moral foundations theory. Although previous studies have suggested that the MFQ subscales are associated with religiosity, basic research has not yet established whether the measure is understood in the same way by believing and nonbelieving individuals. The purpose of this study, therefore, was to examine whether the MFQ (and specifically the purity/sanctity subscale) is understood in the same way by these 2 groups. We predicted that the purity/sanctity subscale would not demonstrate strong (i.e., scalar) invariance. Across 2 samples, we found support for configural and metric invariance and problems with scalar invariance. These results suggest that between-groups differences observed in previous studies may be due to measurement artifacts.