We use Wisconsin Longitudinal Study data (n = 2,678) to assess the effects of religious denomination and ideology on end-of-life treatment preferences in two hypothetical terminal illness scenarios: physical pain and severe cognitive impairment. We found no statistically significant differences when comparing traditionally defined religious denominational groups (i.e., conservative, moderate and liberal Protestants; Catholics; other religions; no religion). However, when we considered the intersection of broad denominational group and adherence to Christian fundamentalist beliefs, we found that fundamentalist Catholics and fundamentalist Protestants were significantly more likely than their nonfundamentalist counterparts to desire life-extending treatments in both scenarios. These effects were fully explained by beliefs about quality of life and religious control over medical decisions. We end with a discussion of the study's theoretical and policy implications.