The implementation of smoke-free policies for workplaces and their impacts have been far from satisfactory. We investigated smoking prevalence in various occupations using data (n = 9283) from the Korea National Health and Nutrition Examination Survey collected from 2008 to 2010. Young adults who were working in the occupation categories of "service and sales," "skilled agricultural, fishery, and forest workers," and "crafts and machine operation" for men and "service and sales" for women showed 1.8 to 7.1 and 3.7 times higher (P < .05) smoking prevalence compared with the reference (managers and professionals), respectively, and the highest prevalence among the 7 occupational categories that were studied. Drinking and stress level were positively associated with being current smokers. We provide quantitative evidence supporting clinicians and policy makers wishing to establish smoking-cessation programs in workplaces for young adults in South Korea, and evidence supporting the improvement of prevention by the concomitant reduction of risk factors.