Objective: To measure the prevalence of pain in women having undergone treatment for breast cancer, to characterize their presentation, and to assess the influence that pain and cancer stage have on quality of life. Materials and methods: A descriptive, observational, cross-sectional analytical study in 328 patients with breast cancer from the National Institute of Neoplastic Diseases. The SF-36 Health-Related Quality of Life questionnaire and a scale designed to measure pain were used. Results: In all, 87.8 % had pain; severe pain when loading objects, 36.1 % and when exercising, 26.4 %. The mean total quality of life score for all patients was 58.2 ± 19.2. There was a significant inverse correlation between pain and quality of life. Patients with breast cancer and pain had physical function impairment in different clinical stages. Conclusions: Half of breast cancer patients had moderate to severe pain. There were significant statistical differences between patients with pain and without pain in health-related quality of life. Clinical stage 0 had a strong correlation with impairment of social function, and clinical stage IV had a strong correlation with the Emotional Role dimension. Patients with metastases had physical function more severely affected with a low SF-36 score; the same was the case with body pain, vitality, and general health.