Approximately half of those receiving treatment for an alcohol use disorder (AUD) also suffer with an anxiety or depressive (internalizing) disorder. Because all internalizing disorders mark a poor alcohol treatment outcome, it seems reasonable to supplement AUD treatment with a psychiatric intervention when these disorders co-occur with AUD. However, this conclusion may be faulty given that the various possible interrelationships between AUD and internalizing disorders do not uniformly imply a high therapeutic yield from this approach. Unfortunately, the studies conducted to date have been too few and too small to resolve this important clinical issue with confidence. Therefore, we used a meta-analytic method to synthesize the effects from published randomized controlled trials examining the impact of supplementing AUD treatment with a psychiatric treatment for co-occurring internalizing disorder (N = 15). We found a pooled effect size (d) of .32 for internalizing outcomes and .22 for a composite of alcohol outcomes; however, the alcohol outcomes effect sizes were greater than this for some specific outcome domains. Subgroups that differed in terms of internalizing outcomes included treatment type (medication vs. cognitive behavioral therapy) and treatment focus (anxiety vs. depression). There was also a trend for the studies with better internalizing disorder outcomes to have better alcohol outcomes. These results indicate that clinical outcomes (both psychiatric and alcohol-related) could be somewhat improved by supplementing AUD treatment with psychiatric treatment for co-occurring internalizing disorder. (Am J Addict 2011;00:1–11)