To examine rates of smoking and tobacco treatment utilization by insurance coverage status (Medicaid, commercial, exchange) among newly enrolled patients in the post Affordable Care Act (ACA) era. We examined new members who enrolled in Kaiser Permanente Northern California through Medicaid, the California exchange, or nonexchange commercial plans (N=122,298) in the first 6 months of 2014 following ACA implementation. We compared these groups on smoking prevalence and tested whether smokers in each group differed on sociodemographic characteristics and in their utilization of tobacco treatment (pharmacotherapy and counseling) in 2014. Smoking prevalence was higher among Medicaid (22%) than exchange (13%) or commercial (12%) patients (P<0.0001). Controlling for key sociodemographic and clinical characteristics, Medicaid (odds ratio, 1.49; 95% confidence interval, 1.29-1.73) smokers had greater odds of tobacco treatment use than commercial smokers. Other groups at risk for underuse included men, younger patients, Asians, and Latinos. In this cohort of newly enrolled patients after ACA implementation, Medicaid patients were more likely to be smokers compared with exchange and commercial patients, but they were also more likely to use tobacco treatment. Low tobacco treatment use among exchange and commercial plan smokers, as well as younger men, Asians and Latinos poses a significant obstacle to improving public health and additional targeted outreach strategies may be needed to engage these patients with available health services.