© 2015 American College of Occupational and Environmental Medicine. Objective: This study examines the association between environmental tobacco smoke (ETS) exposure and atrial fibrillation (AF). Methods: We examined the cross-sectional association between ETS exposure and AF in 12,021 participants (mean age: 659.9 years; 60% women; 40% blacks) from the REasons for Geographic And Racial Differences in Stroke study who self-identified as never smokers between 2003 and 2007. Results: A total of 2503 (21%) participants reported ETS exposure. In a multivariate logistic regression model adjusted for sociodemographics and potential confounders, ETS exposure was significantly associated with AF (odds ratio=1.27, 95% confidence interval=1.08, 1.50). Conclusions: Our findings suggest that the harmful effects of ETS exposure extend to sustained arrhythmias such as AF.