This cross-sectional study was conducted to verify self-efficacy, self-esteem, and social support as characteristics of health promotion behavior in middle-aged Koreans, and the influence of social support on self-efficacy and self-esteem with respect to health promotion behavior. Data were collected from 310 subjects in South Korea using a self-administered questionnaire. We found a significant finding that self-efficacy positively influences health promotion behavior, focusing on the moderating effect of social support. Self-efficacy affected health promotion behavior (P < 0.01) as did social support. Mean self-efficacy, self-esteem, health promotion behavior, and social support scores were 50.27, 29.35, 124.39, and 76.51, respectively. This finding provides strong evidence that social support can be used as a model to understand health promotion behavior. Individualized nursing interventions based on social support and self-efficacy theory should be utilized in high-risk middle-aged patients so as to assist and improve health promotion behavior. Also, in community practice settings, nurses should consider that increased social support and self-efficacy are required to improve health promotion behaviors.