Background: This study examined whether immigrants were less likely to be covered by a smoke-free workplace policy and whether workplace smoking policies garnered comparable associations with smoking for immigrants and for those born in the USA. Methods: Investigators applied multiple logistic regression to the 2001-2 Current Population Survey Tobacco Use Supplement among US indoor workers (n = 85 784). The study examined first, whether nativity (immigrants vs US born) was independently associated with smoke-free policy coverage, and second, whether the smoke-free policy association with current smoking was differential by nativity (effect modification). Results: Immigrants were less likely to work in smoke-free workplaces than those born in the USA; however, occupation and industry accounted for these disparities. Employment in a workplace that was not smoke free was associated with higher odds of smoking (vs smoke-free workplaces), both before (OR 1.83, 95% CI 1.74 to 1.92) and after (OR 1.36, CI 1.29 to 1.44) covariate adjustment among the US born, but associations were weaker among immigrants (OR 1.39, CI 1.20 to 1.61, unadjusted; OR 1.15 CI 0.97 to 1.35 adjusted). Worker industry partly explained (16% of) the weaker policy-smoking association among immigrants, while other socioeconomic variables reduced the policy-smoking association without explaining the disparity. Conclusions: The patchwork of US workplace smoking restriction policy at different governmental levels, combined with a voluntary regime among some employers, generates coverage inequalities. Workplace smoke-free policies may be less effective for immigrants, and this is related to differential coverage by such policies due to occupational segregation. Understanding the complex patterns of the social context of smoking is important for understanding how policy interventions might have heterogeneous effects for different demographic groups.