In general, the pattern and perception of complementary and alternative medicine (CAM) use in young people are little known. Particularly, given South Korea’s dual health care system that includes both Korean traditional medicine and Western medicine, young adults in South Korea may be unique for the study of CAM use. Accordingly, this study investigated the modality, purpose, and perceptions of CAM use among young adults in South Korea and determined the predictors of CAM use. In addition, reasons for CAM use were compared to those for exercise. A survey was conducted among 649 young members of fitness centers (aged 20-39 years). The structured written questionnaire included the questions related to use of 30 CAM modalities, satisfaction with CAM use, factors associated with CAM use, reasons for exercise and CAM use, and perceptions of CAM. The most common therapies used in lifetime were acupuncture, massage, moxibustion/cupping, yoga, and diet-based therapies. The most satisfied therapy was massage followed by aroma therapy. The main reasons for using CAM were to relieve musculoskeletal pains while those for doing exercise were to lose weight, to promote health, and to have a positive body image. Multiple logistic regression analysis revealed that higher education level, having a religion, and having a health problem were significant independent predictors of CAM use after controlling for other factors. The majority of respondents reported “relief of pain and symptoms” as the perceived effect of CAM and “lack of advertising” as the weakness of CAM. The majority of respondents got CAM information from mass media and Internet. In conclusion, CAM use is significantly associated with education level, religious status, and health status in Korean young adult members of fitness centers. The main purposes of utilizing CAM and performing exercise are different.