Who benefits most from helping others? Previous research suggests that common polymorphisms of the oxytocin receptor gene (OXTR) predict whether people behave generously and experience increases in positive mood in response to socially focused experiences in daily life. Building on these findings, we conducted an experiment with a large, ethnically homogenous sample (N = 437) to examine whether individual differences in three frequently studied single nucleotide polymorphisms of OXTR (rs53576, rs2268498, rs2254298) also predict differences in the positive mood benefits of financial generosity. Consistent with past research, participants who were randomly assigned to purchase items for others (vs. themselves) reported greater positive affect. Contrary to predictions, using Bayesian statistics, we found conclusive evidence that the benefits of generosity were not moderated by individual differences in OXTR single nucleotide polymorphisms. The current work highlights the importance of publishing null results to build cumulative knowledge linking neurobiological factors to positive emotional experiences. (PsycInfo Database Record (c) 2020 APA, all rights reserved).