If Supreme Court behavior is structured largely by the policy preferences of the justices, political scientists ought to consider the source of those preferences. Religion is one force that can strongly shape a judge’s worldview and therefore her or his votes. In this article, the author examines the effect of religion on U.S. Supreme Court votes in eleven issue areas plausibly connected to religious values. Catholic justices vote in ways that more closely adhere to the teachings of the Catholic Church than do non-Catholic justices even after controlling for ideology. These results may indicate that Catholic theology is different from Protestant or Jewish theology. It is also possible that on some issues there is not much of a theological difference, but religious values play a more prominent role in public life for Catholic justices.