Four studies examine the social cognitive mechanisms through which sacred values produce social schisms, focusing on the role of metadehumanization. Using hypothetical scenarios, Studies 1 and 2 demonstrate that violators of sacred values feel dehumanized by value holders and reciprocate this dehumanization. Using real sacred values, Studies 3 and 4 show similar effects. Study 3 further controls for the effects of mere disagreement and finds participants felt more dehumanized when family members disagreed with them in discussions of sacred values compared to preferences. Study 4 examined the sacralization of mask-wearing during the COVID-19 pandemic, finding that the inflammatory effect of sacralization on hostility was in part explained by metadehumanization, leading to greater reciprocal dehumanization, thus fueling conflict. In conclusion, results suggest metadehumanization may underlie the often explosive nature of sacred conflict.