The aim of this study is to examine the effect of fibromyalgia (FM) treatment on mastalgia by performing fibromyalgia screening in patients who applied for mastalgia and whose underlying cause could not be found. Patients who applied to Kocaeli University General Surgery Outpatient Clinic between November 2017 and November 2020 with breast pain were included (n=120). Patients without cancer, systemic disease, previous breast surgery, and breast mass larger than 3 cm (n=30) were referred to the Physical Therapy and Rehabilitation Outpatient Clinic. A total of 13 patients (43%) were diagnosed with FMS. Twelve of them were given selective serotonin-noradrenaline reuptake inhibitor (duloxetine) treatment for 3 months. Turkish version of the Short Form - 36 (SF-36) quality of life scores, Visual Analog Scale (VAS), Cardiff breast pain score before and after treatment were compared. The remaining 17 patients were followed as only mastalgia. Patients with fibromyalgia and mastalgia had similar demographic results. At the end of the 3rd month, the complaints of breast pain completely regressed in all of the patients. Statistically significant changes were detected in VAS score, the number of trigger points, and SF-36 quality of life scores, Cardiff breast pain score after duloxetine treatment. In the presence of unexplained mastalgia, fibromyalgia should be kept in mind. Duloxetine treatment improved the breast pain and quality of life in patients with mastalgia and fibromyalgia.