National injustice has been linked to lower national happiness. We predict that national religiosity will mitigate this negative influence of injustice on happiness. We test this hypothesis analyzing national-level data from 121 nations, using a single-level moderated regression analysis. To capture various aspects of national injustice, we combine four national measures associated with injustice, namely: indexes of group grievances, political terror, rule of law, and corruption perceptions. The results show that national religiosity has a significant moderating effect on the relationship between injustice and happiness, such that higher levels of religiosity mitigate more of the negative effects of injustice on happiness than lower levels do. The results hold when religious affiliation and indexes of economic prosperity, education, and social support are controlled for. These results indicate that people in religious cultures may successfully utilize religious faith to deal with adverse conditions.