It is important to know how well patients with type 2 diabetes understand and use health information available online in relation to health-promoting behaviors. Thus, the purposes of this study were to examine the association among electronic health literacy, perceived benefits, self-efficacy, and health-promoting behaviors in patients with type 2 diabetes, and to identify factors that affect health-promoting behaviors. A cross-sectional survey was conducted in a diabetes center in Seoul, South Korea. It was found that health-promoting behaviors were significantly correlated with electronic health literacy (r = 0.15, P < .05), perceived benefits (r = 0.15, P < .05), and self-efficacy (r = 0.47, P < .01). In the multiple linear regression analysis to identify the factors influencing health-promoting behaviors, electronic health literacy (β = .13, P = .040) and self-efficacy (β = .38, P < .001) were found to be significant factors, even after adjusting for general and disease-related characteristics. Strategies to improve health-promoting behaviors in patients with type 2 diabetes should focus on analyzing levels of electronic health literacy and deepening their understanding of online information accordingly.