<p><b>Objectives:</b> We evaluated the long-term (52 weeks) safety and effectiveness of iguratimod (IGU) in patients with rheumatoid arthritis (RA).</p> <p><b>Methods:</b> This multicenter, prospective, observational study included all evaluable RA patients who received IGU since its market launch in 2012. We evaluated adverse events (AEs); adverse drug reactions (ADRs); ADRs of special interest, including liver and renal dysfunctions, interstitial lung disease, gastrointestinal and blood disorders, and infection; and change in Disease Activity Score 28-C-reactive protein (DAS28-CRP) at week 52.</p> <p><b>Results:</b> Safety and effectiveness were analyzed in 2666 and 1614 patients, respectively. The incidences of AEs, serious AEs, ADRs, and serious ADRs were 46.92, 7.35, 38.26, and 4.58%, respectively. The incidence of ADRs peaked at approximately 4 weeks of treatment. Subsequently, the ADR incidence did not increase over time. Improvement of RA activity was shown up to week 52.</p> <p><b>Conclusion:</b> Long-term treatment with IGU in patients with RA resulted in a tolerable safety profile and an improvement in RA activity. IGU could be considered a useful treatment option for patients with RA.</p