Objective: Motivational interviewing (MI) is a treatment approach that has been widely examined as an intervention for tobacco dependence and is recommended in clinical practice guidelines. Previous reviews evaluating the efficacy of MI for smoking cessation noted effects that were modest in magnitude but included few studies. The current study is a comprehensive meta-analysis of MI for smoking cessation. Method: The meta-analysis included 31 controlled trials with an abstinence outcome variable. Studies with nonpregnant (N = 23) and pregnant samples (N = 8) were analyzed separately. Results: For nonpregnant samples, combined results suggest that MI significantly outperformed comparison conditions at long-term follow-up points (dc = .17). The magnitudes of this result represented a 2.3 difference in abstinence rates between MI and comparison groups. All analyses investigating the impact of moderating participant, intervention, and study design characteristics on outcome were nonsignificant, with the exception of studies including international, non-U.S. samples, which had larger effects overall. Several subgroups of studies had significant combined effect sizes, pointing to potentially promising applications of MI, including studies that had participants with young age, medical comorbidities, low tobacco dependence, and, consistent with clinical practice guidelines, low motivation or intent to quit. Effects were smaller among pregnant samples. In addition, significant combined effect sizes were observed among subgroups of studies that administered less than 1 hr of MI and among studies that reported high levels of treatment fidelity. Conclusions: The results are interpreted in light of other behavioral approaches to smoking cessation, and the public health implications of the findings are discussed. © 2010 American Psychological Association.