In the current research we tested a comprehensive model of spirituality, religiosity, compassion, and altruism, investigating the independent effects of spirituality and religiosity on compassion and altruism. We hypothesized that, even though spirituality and religiosity are closely related, spirituality and religiosity would have different and unique associations with compassion and altruism. In Study 1 and 2 we documented that more spiritual individuals experience and show greater compassion. The link between religiosity and compassion was no longer significant after controlling for the impact of spirituality. Compassion has the capacity to motivate people to transcend selfish motives and act altruistically towards strangers. Therefore, we reasoned that spirituality (but not religiosity) would predict altruistic behavior and that compassion would help explain this link. Indeed, in Studies 3, 4, and 5 we found that more spiritual individuals behaved more altruistically in economic choice and decision-making tasks, and that the tendency of spiritual individuals to feel greater compassion mediated the spirituality-to-altruism relationship. In contrast, more religious participants did not consistently feel more compassion nor behave more altruistically. Moreover, in Studies 3 and 4 we found that the broader traits of Agreeableness, Openness, and Extraversion did not help explain why more spiritual individuals behaved more altruistically. Our findings argue that spirituality—above and beyond religiosity—is uniquely associated with greater compassion and enhanced altruism towards strangers.Keywords: altruism, behavioral economics, religion, spirituality, compassio