Religions instruct individuals to engage in prosocial behaviors. Previous studies are lacking on a positive relation between religiousness and blood donation. We tested this hypothesis using a national survey of 7611 women and 4282 men aged 18-44 years. In women, positive associations of childhood religious affiliation, current affiliation and attendance with blood donation were seen on bivariate analysis but were no longer significant when socio-demographic variables were controlled for. Religiousness was not associated with history of blood donation in men, with the exception of higher donation rates in Catholic men aged 35-44.