Four studies tested the hypothesis that a weaker belief in free will would be related to feeling less gratitude. In Studies 1a and 1b, a trait measure of free will belief was positively correlated with a measure of dispositional gratitude. In Study 2, participants whose free will belief was weakened (vs. unchanged or bolstered) reported feeling less grateful for events in their past. Study 3 used a laboratory induction of gratitude. Participants with an experimentally reduced (vs. increased) belief in free (...) will reported feeling less grateful for the favor. In Study 4, a reduced (vs. increased) belief in free will led to less gratitude in a hypothetical favor scenario. This effect was serially mediated by perceiving the benefactor as having less free will and therefore as being less sincerely motivated. These findings suggest that belief in free will is an important part of being able to feel gratitude. (shrink)