Background: Smoking, including environmental tobacco smoke (ETS) exposure is a well-known risk factor for diabetes. Low socioeconomic status, especially lack of education, also is a risk factor for diabetes. Therefore, we assessed the association of education and smoking status, including ETS exposure, with the prevalence of diabetes. Methods: Data were from the 2007–2013 Korea National Health and Nutritional Evaluation Survey (KNHANES). Multivariable logistic regression examined associations between various lifestyle and health factors and prevalence of diabetes while controlling for potential confounding variables. Subgroup analysis was performed according to smoking status to determine factors associated with diabetes. Results: Of 19,303 individuals analyzed, 1,325 (11.4%) had diabetes. Greater average age, male sex, lower educational level, unemployment, and coexisting health problems were significantly associated with diabetes. Individuals with only elementary, middle, or high school level education had significantly greater odds ratios (p<0.05) compared to college graduates; smokers and nonsmokers exposed to ETS had significantly greater OR (p<0.05) than nonsmokers unexposed to ETS. Subgroup analysis of diabetics according to smoking status revealed significant associations (p<0.05) for diabetic nonsmokers exposed to ETS with female sex, single status, elementary level education, urban residence, National Health Insurance (NHI), hypertension, no alcohol intake, and no moderate physical activity. For diabetic smokers, there were significant associations (p<0.05) with elementary education, urban residence, lack of moderate physical activity, no alcohol intake, and NHI. Conclusions: The results suggested that smoking status, including ETS exposure, was associated with a higher prevalence of diabetes especially in populations with less education. Thus, we should direct efforts for controlling diabetes toward individuals with lower levels of education, and those who are smokers and nonsmokers exposed to ETS.