Objective: This study aims to determine the frequency offibromyalgia syndrome (FMS) among patients with primary Sjögren’ssyndrome (pSS), and the relationship between FMS and the parametersindicating disease activity. Material and Methods: Fifty patients witha diagnosis of Sjögren's syndrome, aged 18-75, were included in thisprospective, cross-sectional study. The demographic characteristics ofthe patients, regular medications and the routine erythrocyte sedimentation rate (ESR) values measured when they came for examination wererecorded. The 2013 American College of Rheumatology (ACR) fibromyalgia criteria were applied to all patients and the EULAR Sjögren'sSyndrome Patient Reported Index (ESSPRI) was applied to evaluate Sjögren's syndrome disease activity. The frequency of patients diagnosedwith FMS according to the 2013 ACR criteria was calculated. The patients were divided into 2 groups according to whether they had FMS ornot. The ESSPRI scores and ESR were statistically analyzed betweenthe groups. Results: FMS was detected in 42% of 50 patients with pSS.The mean ESSPRI score and scores for the fatigue and pain parameterswere significantly higher in patients with FMS (p<0.05), while no significant difference was found in the dryness parameter (p>0.05). Themean ESR was significantly higher in patients with FMS (p<0.05). Conclusion: The results of this study show that FMS is seen at a high ratein patients with pSS and this may negatively affect the disease activity.We think that clinicians should be aware of the possible relationship between FMS and pSS and the need to treat both conditions simultaneously.