While there is considerable agreement that religion can bolster the legitimacy of governments, those who oppose them, and just about any political action by any individual or group, there has been no previous large-N cross-sectional study of the subject. This study tests the effects of religious legitimacy on grievance formation by ethnic minorities using data on 105 ethno-religious minorities from the Minorities at Risk Phase 3 dataset as well as data on religion collected independently. For operational purposes, a minority is an ethno-religious minority when at least 80% of that group's members are of different religious denominations than that of the dominant ethnic group of the state in which they live. The findings show that religious legitimacy does influence grievance formation but that influence is not the monolithically positive influence that would be expected. Religious legitimacy tends to facilitate the formation of grievances over non-religious issues when religion is not an issue in the conflict but deters the formation of grievances over these issues when religion is an issue. The presence of religious legitimacy is also positively associated more indirectly and weakly with the formation of religious grievances.