PURPOSE The Suppression of Ovarian Function trial showed improved disease control for tamoxifen plus ovarian function suppression (OFS) compared with tamoxifen alone for the cohort of premenopausal patients who received prior chemotherapy. We present the patient-reported outcomes. PATIENTS AND METHODS The quality-of-life (QoL) analysis includes 1,722 of 2,045 premenopausal patients with hormone receptor-positive breast cancer randomly assigned to receive adjuvant treatment with 5 years of tamoxifen plus OFS or tamoxifen alone. Chemotherapy use before enrollment was optional. Patients completed a QoL form consisting of global and symptom indicators at baseline, every 6 months for 24 months, and annually during years 3 to 6. Differences in the change of QoL from baseline between the two treatments were tested at 6, 24, and 60 months with mixed models for repeated measures with and without chemotherapy and overall. RESULTS Patients on tamoxifen plus OFS were more affected than patients on tamoxifen alone by hot flushes at 6 and 24 months, by loss of sexual interest and sleep disturbance at 6 months, and by vaginal dryness up to 60 months. Without prior chemotherapy, patients on tamoxifen alone reported more vaginal discharge over the 5 years than patients on tamoxifen plus OFS. Symptom-specific treatment differences at 6 months were less pronounced in patients with prior chemotherapy. Changes in global QoL indicators from baseline were small and similar between treatments over the whole treatment period. CONCLUSION Overall, OFS added to tamoxifen resulted in worse endocrine symptoms and sexual functioning during the first 2 years of treatment, with variable magnitudes of treatment differences. Short-term differences in symptom-specific QoL, treatment burden, and coping effort between treatment groups were less pronounced for patients with prior chemotherapy, the cohort that benefited most from OFS in terms of disease control.