Background and ObjectivesGambling is highly comorbid with disordered use of tobacco and other drugs, and may increase relapse risk among substance use disorder (SUD) patients. We investigated associations between gambling and tobacco use behaviors among SUD patients to inform clinical care.MethodsPatients (N = 651, 170 female) from 25 residential SUD treatment programs in California completed surveys about tobacco use, health, and gambling. Using multivariate regression, we examined associations between gambling, tobacco use behaviors, and mental and physical health.ResultsPast‐year gamblers were more likely than non‐gamblers to be current smokers (adjusted odds ratio [AOR] = 1.44, 95% confidence interval [CI] = 1.03, 2.01). Smokers who gambled had higher mean Heaviness of Smoking Index (HSI) scores (mean difference = +0.32, 95% CI = 0.04, 0.60), and more often reported smokeless tobacco use (AOR = 1.73, 95% CI = 1.16, 2.58), compared to non‐gambling smokers. Past‐year problem gamblers were more likely than all others (non‐gamblers and non‐problem gamblers) to be current smokers (AOR = 1.44, 95% CI = 1.08, 1.90) and to report high psychosocial stress (AOR = 1.87, 95% CI = 1.34, 2.61). Smokers with problem gambling also had higher HSI scores (mean difference = +0.54, 95% CI = 0.14, 0.95) compared to smokers without problem gambling.Discussion and ConclusionsGambling and problem gambling were associated with tobacco use and heavier smoking. SUD patients with gambling comorbidity may be heavier smokers and may need concurrent treatment for tobacco use and problem gambling.Scientific SignificanceThis study provides novel data regarding gambling and tobacco use behaviors among SUD patients.