Previous research has found that religiosity may protect against risky alcohol and drug use behaviors among adolescents, but the social mechanics underpinning the relationship are not well understood. This study examined the relationship between religiosity, heavy drinking, and social norms among U.S. adolescents aged 12 to 17 years, using the 2007 National Survey on Drug Use and Health (n = 14,556). Based on a vicarious learning networks theoretical perspective, the effect of religiosity on heavy drinking behavior was hypothesized to be exerted indirectly through the norms of key reference groups in the social network (close friends and parents). Support was found for reference group norms as one underlying mechanism of the religiosity-alcohol relationship. Religiosity and nonpermissive drinking norms of parents, close friends, and peers maintained a strong protective association with adolescent heavy drinking. Supplementary analyses elaborated on the role of competing and complementary normative orientations among reference groups in the social network. (Contains 1 note, 3 tables and 1 figure.)