Heavy alcohol use frequently co-occurs with cigarette smoking and may impede smoking cessation. This clinical trial examined whether smoking cessation treatment that incorporates brief alcohol intervention can improve smoking cessation outcomes (7-day verified point prevalence abstinence) and reduce drinks consumed per week. Heavy drinkers seeking smoking cessation treatment were assigned by urn randomization to receive, along with 8 weeks of nicotine replacement therapy, either a 4-session standard smoking cessation treatment (ST, n = 119) or standard treatment of equal intensity that incorporated brief alcohol intervention (ST-BI, n = 117). Across follow-ups over 26 weeks, participants in ST-BI reported approximately 20% fewer drinks per week (p less than 0.027) and greater smoking abstinence (adjusted odds ratio = 1.56; 95% confidence interval = 1.01, 2.43) than did those in ST; however, effects on smoking were primarily evident at 2 weeks after quit date and were essentially absent by 16 weeks. The effect of ST-BI on smoking outcome was most robust among moderately heavy drinkers compared with that on very heavy drinkers. Integrating brief alcohol intervention into smoking cessation treatment appears feasible, but further development is needed to yield lasting effects on smoking.