Objective: To assess the effectiveness of osteopathic intervention (OI) and general osteopathic treatment (GOT) in individuals with fibromyalgia syndrome (FMS). Methods: The trial was designed as a randomized controlled trial with 2 osteopathic interventions and 1 untreated control group. The patients in the two osteopathic groups received 10 osteopathic treatments (OI or GOT) within a time period of 12 weeks. The control group did not receive any osteopathic treatment. The primary outcome was the average pain intensity (API) assessed by visual analog scale (VAS). Secondary outcomes were the pressure-pain threshold rated by means of a tender point score, and disease severity, assessed by the Fibromyalgia Impact Questionnaire (FIQ). Results: 50 patients were randomized. The primary outcome parameter API decreased from 7.2 to 4.7 in the OI group, from 6.3 to 4.3 in the GOT group, and increased slightly in the control group from 6.2 to 6.6. There were significant differences for the change in API between the OI group and the control group (VAS: 2.9, 95% confidence interval (CI) = 1.12-4.52), and between the GOT group and the control group (VAS: 2.4, 95% CI = 0.65-4.11), but no significant differences between the OI group and the GOT group. There were no significant differences for the secondary outcome parameters between the groups. Conclusion: A series of osteopathic treatments might be beneficial for patients suffering from FMS.