Previous studies have identified the sociodemographic factors associated with e-cigarette use among adolescents in South Korea. However, literature regarding e-cigarette use among adult smokers remains limited in South Korea.Applying four waves (2013-2016) of The Korea National Health and Nutrition Examination Survey (n = 3227), sociodemographic factors were included in the multivariable logistic regression model to study their relationships with e-cigarette use among adult daily smokers.E-cigarette use increased from approximately 21.2% to 34.6% from 2013 to 2016, respectively. Females had lower odds of e-cigarette use (adjusted odds ratio [AOR] = 0.76; 95% CI, 0.58-0.99, P < .05) compared with males. Older age was negatively associated with e-cigarette use experience (all Ps < .01). Daily smokers with high school education or above all had higher odds of using e-cigarettes compared those with elementary school education (all Ps < .05).As this study examined the trends of e-cigarette use and factors associated with e-cigarette use among adult daily smokers in South Korea, further research is needed to investigate the long-term effect of e-cigarette use on smoking cessation in South Korea as well as other Asian countries.