Several pharmacological and non-pharmacological modalities have been proposed for the treatment of fibromyalgia syndrome (FMS), a common rheumatic disease. Pregabalin is suggested as a first-step medication for FMS in the newest guidelines. Drowsiness, dizziness, and peripheral edema are well-known side effects of pregabalin; however, mastalgia is rarely seen. Presently described is a case of FMS in a patient who developed mastalgia and hyperprolactinemia (HPL) while taking pregabalin.