Background: Rheumatoid arthritis (RA) is a multifactorial autoimmune illness that causes symmetric polyarthritis and can result in deformities in addition to several extra articular manifestations. Galectin-3 is a protein involved in modulating inflammation and apoptosis. The objective of this workis to measure the serum level of Galectin-3 in RA patients and to assess its correlation with disease activity. Methods: A case control study was carried on 66 subjects, 33 RA patients (28 females and 5 males), and 33 healthy subjects, taken as control (23 females and 10 males). Disease Activity score (DAS28) was estimated for RA patients. Blood samples from patients and controls were tested for Galectin-3. Results: Serum Galectin-3 levels were substantially greater (P<0.001) in RA patients than in controls as it ranged between (2.3-33.6 ng/ml vs 5.21-9.67 ng/ml P<0.001). Serum Galectin-3 correlated with DAS28 (r=0.62, p=<0.00),CRP(r=0.35,p=0.04) also with ESR(r=0.36,p=0.04). Galectin-3 showed a sensitivity of 96.97% and a specificity of 84.85% at a cutoff of 6.95 ng/ml to discriminate RA from controls. Conclusions: Serum Galectin-3 levels were higher in RA patients than controlsand correlated with disease activity So, Galectin-3 can be used as a biomarker for RA disease activity.