More than two third of patients with primary Sjögren's syndrome (SS) report fatigue. Despite its clinical relevance, only a few studies have examined the relationship of fatigue with the presence of an overlapping Fibromyalgia (FM) and other clinical and biological variables. The aim of this study was to assess the relationship between fatigue and SS disease activity and damage, FM, widespread pain, and mood disorders; finally, the possible correlation between fatigue and a panel of cytokines likely to drive the immunopathological process of the disease has been examined. Thirty-five female patients with primary SS were consecutively enrolled; for each patient the Sjögren's Syndrome Disease Damage Index (SSDDI) and the Sjögren's Syndrome Disease Activity Index (SSDAI) were calculated. Patients rated pain, fatigue and disease activity using a 100-mm VAS and completed Health Assessment Questionnaire (HAQ), the Zung depression (ZSDS) and anxiety scales (ZSAS). 30/35 patients (85.7%) felt unduly tired and the same percentage of patients suffered with pain in more than one area of the body. 7 patients satisfied ACR criteria for FM, representing 20% of the whole cohort and 23% of SS patients with fatigue. No differences were found in disease duration, SSDDI, SSDAI, ZSDS and ZSAS among SS patient with or without FM. In the whole group, fatigue VAS correlated with HAQ, ZSAS, ZSDS and pain VAS but not with age, disease duration, presence and severity of arthritis, SSDDI, SSDAI, or cytokines. In conclusion, an overlapping FM can contribute to, but does not entirely account for fatigue in Italian patients with primary SS.