PURPOSE: The purpose of present study was to explore relationship between physical activity (PA) behavior and self-efficacy among older Korean-Americans (OKAs) based on reviewing major theories that are used to understand PA behavior, particularly as they relate to older adults within sociocultural contexts. METHODS: 151 OKAs, living in California, were recruited and interviewed once. Self-efficacy and PA level were measured by Exercise Self-Efficacy Scale, Community Healthy Activities Model Program for Seniors (K-CHAMPS) questionnaire, respectively. RESULTS: 82.8% of OKA women and 72.4% of OKA men had relatively low (38.8+/-29.3) self-efficacy related to PA. Exercise self-efficacy was statistically significant and positively associated with frequency for moderate and greater PA (r = 0.25, p < .01), frequency for all listed PA (r = 0.21, p < .05), caloric expenditure for moderate and greater PA (r = 0.23, p < .01), and caloric expenditure for all listed PA (r = 0.31, p < .01). CONCLUSION: Social Cognitive Theory including self-efficacy can provide insight about how to shape strategies that encourage OKAs to adhere to regular PA because it focuses on environmental as well as personal factors. Increased efforts are needed to understand the other factors associated with being active in OKAs.