Objective To characterize the clinical features, diagnostic pitfalls, and management of Mycobacterium marinum (M. marinum) hand infection in patients with rheumatoid arthritis (RA). Methods We retrospectively analyzed one RA case admitted in 2025 and systematically reviewed Chinese and English publications from 2011 to 2026 to summarize reported cases. Results A 68-year-old woman with RA presented with chronic swelling, pain, and purulent discharge of the right hand. Empirical antibacterial therapy and adjustment of immunosuppressive treatment were ineffective. After multidisciplinary team (MDT) consultation, surgical debridement was performed and deep tissue specimens were obtained. Metagenomic next-generation sequencing (mNGS) identified M. marinum, and histopathology demonstrated granulomatous inflammation. The patient improved after azithromycin plus rifampicin. Ten cases were included in the literature review. Lesions commonly involved tendon sheaths, synovium, or joints and were frequently misdiagnosed as RA flare. Diagnosis mainly relied on targeted culture and/or molecular assays. Most patients achieved remission or stabilization with combination antimycobacterial therapy with or without debridement. Conclusion M. marinum infection affecting tendon sheaths, synovium, or joints can closely mimic RA flare. In immunosuppressed RA patients with refractory hand lesions, early consideration of nontuberculous mycobacterial infection, MDT-based decision-making, deep tissue sampling, and molecular diagnostics facilitate timely etiological confirmation. Prolonged combination therapy and timely debridement may improve outcomes.