Twelve-step self-help organizations maintain that anyone, regardless of his or her religious beliefs, can benefit from participation in their groups. Yet many addiction professionals have reservations about referring nonreligious patients to 12-step groups. The present study examined the influence of patients' religiosity on whether they were referred to and benefited from 12-step groups. Participants were 3,018 male substance abuse inpatients. Individuals who engaged in fewer religious behaviors in the past year were referred to 12-step groups less frequently by clinicians. However, referrals to 12-step groups were effective at increasing meeting attendance, irrespective of patients' religious background, and all experienced significantly better substance abuse outcomes when they participated in 12-step groups. The viewpoint that less religious patients are unlikely to attend or benefit from 12-step groups may therefore be overstated.