Background: Immune system has an important effect on pain-related disorders such as fibromyalgia syndrome (FMS). There is no specific laboratory technique for the diagnosis of FMS, but measuring serum proinflammatory cytokines may help. Objective: The purpose of our study was to determine the serum levels of immune mediators and their relationship with FMS symptoms. Methods: 25 healthy individuals and 29 FMS patients receiving pregabalin 150 mg/day for a minimum of 3 months were included in this study. FMS patients were diagnosed according to diagnostic criteria of the American College of Rheumatology (ACR 2010). Widespread pain index (WSI), fatigue, waking unrefreshed, cognitive symptoms, somatic symptoms, and Fibromyalgia Impact Questionnaire (FIQ) scores were evaluated in patients with FMS. Serum levels of proinflammatory cytokines (IL-2, IL-6, IL-12, IL-17, IFN-γ, TNF-α) were assessed using enzyme-linked immunosorbent assay (ELISA). Results: Proinflammatory cytokine levels were higher in the control group than patients with FMS (p <0.05). A positive correlation was found between age and WSI (P=0.037). In addition, a significant positive relationship was determined between IL-17 level and waking unrefreshed (P=0.049). There was no significant relationship between other cytokines and clinical findings. Conclusion: Lower proinflammatory cytokine levels identified in FMS patients may be related to pregabalin treatment, and there may be an impairment in the inflammatory response. On the contrary, IL-17 showed a positive correlation with waking unrefreshed.