PURPOSE: This cross-sectional study was designed to explore the relationship among social support, experienced stressful life events and health behaviors of Korean undergraduate students, and validate the mediator effect of social support. METHOD: One thousand four hundred fifty-three undergraduate students were randomly selected from five universities located in the middle area of Korea. RESULT: The health behaviors of Korean undergraduates tend to have unhealthy patterns. In the case of the students living without family, experiencing more stressful life events and perceiving lower social support, health behaviors are poor. The relationship between perceived social supports, the frequency of the experienced stressful life events and the score of health behavior patterns is statistically significant. After controlling the effect of social support, the correlation coefficient between the frequency of experienced stressful life events and the score of health behavior patterns was slightly lower. The score of health behaviors between the group with an extremely high score of social support and the group with an extremely low score were statistically significantly different. CONCLUSION: Future studies need to be pursued to develop various strategies such as a health education programs and counseling programs for health maintenance and health promotion of undergraduates.