OBJECTIVE: To evaluate the influence of pain on quality of life in breast cancer patients. METHODS: A cross-sectional study of 400 patients, including 118 without metastasis, 160 with loco-regional metastasis and 122 with distant metastasis. The instruments used were the European Organization for Research and Treatment for Cancer Quality of Life Questionnaire-Core 30 and the Breast Cancer-specific 23 and short McGill Pain Questionnaire. RESULTS: In total, 71.7% of patients reported pain. The most frequent sensory descriptor used by patients was ‘jumping.’ In the evaluative dimension, the main descriptor chosen was troublesome. The Global Health self-assessment showed pain to be inversely correlated with quality of life: the group without metastasis had a mean score of 55.3 (SD=24.8) for those in pain, which rose to 69.7 (SD=19.2) for those without pain (p=0.001). Subjects with loco-regional metastasis had score of 59.1 (SD=21.3) when in pain, and those without pain had a significantly higher score of 72.4 (SD=18.6) (p<0.001). Patients from the distant metastasis group showed similar results with a mean score of 48.6 (SD=23.1) for those in pain and 67.6 (SD=20.4) for those without pain (p=0.002). Regarding the association of pain intensity and quality of life, patients with distant metastasis and intense pain had the worst scores for quality of life with a functional scale mean of 49.9 (SD=17.3) (p<0.009), a Symptom Scale score of 50.0 (SD=20.1) (p<0.001) and a Global Health Scale score of 39.7 (SD=24.7) (p<0.006). CONCLUSIONS: Pain compromises the quality of life of patients with breast cancer, particularly those with advanced stages of the disease.