Children are told that Santa Claus is a real agent who can observe them, judge them, and reward them. Famously, He's making a list, he's checking it twice; He's going to find out who's naughty or nice . Our goal was to determine which factors, if any, influence whether belief in Santa or other traditions associated with the Christmas Festival influence a child’s moral behavior. We conducted a pilot in 2019, then replicated and extended our findings in 2021 and 2022. Overall, we collected analyzable data from 440 UK-based parents who reported on their child’s (ages 4 to 9) behavior at two timepoints: During mid/late November, and the week preceding Christmas Day (December 25). We constructed and refined a tool for parental report of everyday behaviors of children that broadly covers positive/prosocial behavior and negative/antisocial behaviors. We find that a child’s belief alone is insufficient to predict positive behaviors, but that the presence and intensity of Christmas rituals influence positive behavior, and specifically influence unprompted behaviors. Further, a parent’s intention to model Christmas relevant behaviors indirectly affects the child’s behavior. Other potential predictors of behavioral improvements were ruled out, including parents’ mood, whether parents’ explicitly reminded their children of Santa, the amount of free-time and family-time a child had during the Christmas period, and various aspects of religiosity (though our sample was highly secular). We report, for the first time, that a child’s behavior actually improves as Christmas Day approaches, and though the effect is small, it is primarily attributable to participation and exposure to Christmas rituals. These results have practical and theoretical implications for the evolution of moralizing religions in our species.