Balneotherapy (BT) is a complementary therapy widely used in several rheumatic conditions, however, the evidence in hand osteoarthritis (HOA) is still scarce. The aim of this preliminary study is to retrospectively evaluate the symptomatic effects of a cycle of mud-bath therapy in HOA patients. Two hundred twelve outpatients with primary bilateral HOA treated with 12 daily local mud packs and generalized thermal baths with a sulfurous-arsenical-ferruginous mineral water added to usual treatment were included in the study. Each patient was examined at baseline and at the end of thermal therapy (2 weeks). Primary outcome measures were global spontaneous hand pain on a Visual Analogue Scale (VAS) and the Functional Index for Hand Osteoarthritis (FIHOA) score; secondary outcomes were handgrip strength, duration of morning stiffness, Health Assessment Questionnaire (HAQ), Short Form Health Survey (SF-12), tolerability and patients' and physicians' global impression of treatment efficacy and tolerability. Our results demonstrated that the efficacy of mud-bath therapy was significant in all the assessed parameters at the end of therapy, except for the physical component score of SF-12. The thermal treatment was well tolerated. The patient's and the physician's global assessments showed a high level of satisfaction in terms of efficacy and safety. In conclusion, our results may suggest a short-term effectiveness of mud-bath therapy in controlling pain and improving functionality in HOA patients, supporting the role of this treatment as a complementary strategy in the management of HOA; however, further randomized controlled trials with a long-term follow-up are needed.