This study evaluated the benefits of homeopathy on the quality of life (QOL) of patients with nonmetastatic breast cancer (BC). There is an increasing use of homeopathy in patients with BC after diagnosis, leading to an overall decrease in medications that palliate the side effects of cancer treatment. This may indicate that QOL is improved in patients with BC who use homeopathy. Background: Complementary therapy in oncology aims to help patients better cope with the illness and side effects (SEs) of cancer treatments that affect their quality of life (QOL). This study aimed to assess the benefits of homeo- pathic treatment on the health-related QOL (HRQOL) of patients with non-metastatic breast cancer (BC) prescribed in postsurgical complementary therapy. Patients and Methods: An extraction from the French nationwide healthcare database targeted all patients who underwent mastectomy for newly diagnosed BC between 2012 and 2013. HRQOL was proxied by the quantity of medication used to palliate the SEs of cancer treatments. Results: A total of 98,009 patients were included (mean age: 61 ± 13 years). Homeopathy was used in 11%, 26%, and 22% of patients respec- tively during the 7 to 12 months before surgery, the 6 months before, and 6 months after. Thereafter, the use remained stable at 15% for 4 years. Six months after surgery, there was a significant overall decrease (RR = 0.88, confidence interval (CI)95 = 0.87-0.89) in the dispensing of medication associated with SEs in patients treated with ≥ 3 dispensing of homeopathy compared to none. The decrease appeared to be greater for immunostimulants (RR = 0.79, (CI)95 = 0.74- 0.84), corticosteroids (RR = 0.82, (CI)95 = 0.79-0.85), and antidiarrheals (RR = 0.83, (CI)95 = 0.77-0.88). Conclusion: The study showed an increasing use of homeopathy in patients with BC following diagnosis. This use was maintained after surgery and seemed to play a role in helping patients to better tolerate the SEs of cancer treatments.