Although genetic factors underpin individual differences in religiosity, the psychological mechanisms through which such influences are manifested are presently unknown. Religiosity is associated with concerns for community integration and existential certainty, suggesting that heritable influences underlying such sentiments may overlap with heritable influences underpinning religiosity. Here we tested this hypothesis within a genetically informative design, using a large, nationally-representative twin sample. As predicted, heritable effects underlying community integration and existential uncertainty were strongly overlapping with the heritable influences on religiosity. These findings are consistent with the position that individual differences in religiosity are mediated through biological systems involved in meeting both social and existential needs, although further work is required to determine directions of causal action.