Religious studies of fertility typically focus on the effect of religious affiliation on fertility; the role of religiosity in determining fertility remains overlooked. Meanwhile, most studies focus on studying female fertility; whether religion and religiosity have significantly different impacts on men’s and women’s fertility rarely has been examined. To fill these gaps, this study uses data from the 2002 NSFG Cycle 6 on religious affiliation, religiosity, and children ever born (CEB) for both men and women to investigate the effects of religious affiliation and religiosity on male and female fertility. A series of hypotheses which aim to demonstrate the critical role of religiosity, particularly the importance of religious beliefs in people’s daily life in shaping people’s fertility behavior are tested. The findings show a shrinking pattern of fertility differentials among religious groups. However, religiosity, particularly religious beliefs, shows a substantially positive effect on fertility. The gender interaction terms are not significant which indicates that the effects of religion and religiosity on fertility do not vary by gender.