The goal of this study was to compare dietary supplement use between women who received all recommended conventional breast cancer treatments (Receivers) with those who did not (Refusers). We sought to understand commonly used supplements, use frequency, and prescribers. Methods: A secondary analysis was conducted using baseline data of Breast Cancer Integrative Oncology Study, which recruited 369 women with breast cancer from integrative oncology clinics and Cancer Surveillance System registry in Western Washington State. Self-reported data and registry data were analyzed using descriptive statistics, t-tests, and X 2 tests to compare Receivers and Refusers in their demographic and disease characteristics and supplement use. Results: Refusers used more supplements than Receivers did after diagnosis, 5.43 ± 5.29 vs. 2.66 2.88, F = 26.32, p < 0.001. Refusers used more fish oil and garlic before diagnosis, and more green tea, vitamin C, melatonin, coenzyme Q10, turmeric, and garlic after the diagnosis than Receivers. Most Receivers and Refusers took supplements 5 or more days per week. Most of the supplements were self-prescribed except vitamin D and Melatonin, which were prescribed by medical doctors or CAM providers. Conclusions: Receivers and Refusers generally used the same top ten supplements, often antioxidants, although the frequency of use differed slightly, and Refusers took more supplements. Receivers, who are undergoing chemotherapy or radiotherapy need to know that taking antioxidants may influence treatment effectiveness. Refusers need to be informed that there is no strong evidence that the use of dietary supplements reduces recurrence or mortality.