To explore the frequency of fibromyalgia syndrome (FMS) among hospitalized cancer patients and address the relationships between pain, fatigue and quality of life with regard to the extent of pain, a cross-sectional and descriptive study was carried out in the Oncology Supportive Care Unit on 122 hospitalized cancer patients. Pain, sleep, disease impact (Fibromyalgia Impact Questionnaire), fatigue (Brief Fatigue Inventory), quality of life (Short Form 36 and European Organization for Research on Treatment of Cancer questionnaires Quality of Life-C30) were gathered using standardized measures. Thirteen of the hospitalized cancer patients (10.7%) included in the study were diagnosed with FMS. There were no statistically significant differences among three pain groups with respect to demographic characteristics (P > 0.05). There were significant differences among groups with regard to the presence of metastasis, fatigue, sleep disorder, pain, Brief Fatigue Inventory, Fibromyalgia Impact Questionnaire, most of subscores of Short Form 36 and European Organization for Research on Treatment of Cancer questionnaires Quality of Life-C30 scores (P < 0.05). In the present study, we have calculated the frequency of FMS among patients admitted to the oncology hospital in addition to establishing the relationships between pain, fatigue and quality of life with regard to the extent of pain. We believe that the descriptive data presented in this study would be helpful in future studies and therapeutic approaches.