This study investigated the association between extent of lifetime attendance in Alcoholics Anonymous (AA) and spiritual gains among treatment seeking adults for alcohol use disorder. Participants included 246 individuals from 2 of the 3 sites in the Relapse Replication and Extension Project (Lowman, Allen, Stout, & The Relapse Research Group, 1996). Baseline characteristics included 63% male, 39.9% single, and the average age was 34 years (SD = 8.2). The Alcoholics Anonymous Involvement questionnaire (Tonigan, Connors, & Miller, 1996) was used to assess lifetime AA attendance. The Religious Beliefs & Behaviors Questionnaire (Connors, Tonigan, & Miller, 1996) was used to assess spirituality. Percent days abstinent (PDA) and drinks per drinking day (DPDD) were measured using the Form 90. At baseline, adults with more extensive AA histories were more severely alcohol impaired although they were no older relative to adults with less past AA exposure. Clear patterns of AA engagement were found between the high–low AA history groups over follow-up, with adults with less AA experience reporting less AA participation across a swath of AA-specific measures. Gains in spiritual practices significantly mediated AA-related benefit as measured by PDA and DPDD. Tests for moderated-mediation indicated that the magnitude of the mediational effect of spiritual gains did not differ between high–low AA history groups. Having an extensive AA history did not advantage (or disadvantage) adults in mobilizing future spiritual practices that are prescribed in AA. Clinical assessment of client AA history is important, however, because it predicts both the nature and extent that clients may participate in AA.