Purpose: To examine the levels of physical activity (PA) and diet quality, socio-demographic and clinical correlates, and identify associations with health-related quality of life (HRQOL) among breast cancer survivors. Methods: The study used a cross-sectional study design. A total of 74 breast cancer survivors who had completed their primary cancer therapy were recruited from a comprehensive cancer center in Korea. Measurements used included the International Physical Activity Questionnaire, the Diet Quality Index, and the EORTC QLQ-C30. Results: Only twenty-six women (35.1%) met the American Cancer Society criteria of weekly PA, while most participants (93.2%) displayed good or excellent diet quality. Those less likely to meet the PA criteria were older women, women who had a lower economic level, and women not receiving anti-hormone therapy. However, there was no significant factor associated with diet quality. Women who met the criteria for PA displayed significantly better global QOL than women who did not meet the criteria. No significant differences were found in HRQOL between women who did and did not meet the diet quality criteria. Conclusion: Nurses should be aware of breast cancer survivors who are older and who have a low economic status when assessing and screening the level of PA to improve HRQOL.