PURPOSE: The purpose of this study was to identify changes of supportive care needs and relationship to quality of life (QOL) in patients with breast cancer. METHODS: 117 patients with breast cancer were administered the Supportive Care Needs Survey-Short form 34 and the Functional Assessment of Cancer Therapy-Breast before adjuvant therapy after mastectomy (T1), at the end of completing adjuvant therapy (T2), as well as 6 months after the completion of adjuvant therapy (T3). Data were analyzed using SPSS/Win 21.0. RESULTS: The highest unmet supportive care needs were observed in the health system and information domain and the psychological domain at each time point. The health system and information (F=22.49, p<.001) and physical and daily living needs (F=5.72, p=.004) were higher at T1 and T2 than T3. The psychological (F=7.43, p=.001) and patient care and support needs were higher at T1 than T2 and T3. Multiple regression analysis showed that breast cancer patients with greater physical and daily living and psychological needs were significantly associated with poorer QOL at all times. CONCLUSION: Supportive care should be timely provided to breast cancer patients to improve their ability to cope with physical and psychological problem and QOL. Breast cancer patients who had more unmet needs in psychological and physical domains were more likely to have a poor QOL.