Objectives: Rheumatoid arthritis (RA) is a common chronic inflammatory arthropathy of unknown etiology. Trace elements have a great role in a number of biological processes. The aim of this study was to assess the serum element boron in a sample of Iraqi patients with RA and to evaluate its relationship if present with disease activity, functional class of the disease, and rheumatoid factor (RF). Methods: A cross sectional study enrolled 107 RA patients and 214 controls matched in age and sex. The American College of Rheumatology 1987 revised criteria was used for diagnosis of RA. Disease Activity Score index of 28 joints (DAS28), functional class of RA patients, RF, erythrocyte sedimentation rate (ESR) were measured in patients' group; serum boron levels were measured using a flame atomic absorption spectrophotometer in both patients and controls groups. Results: RA patients had significantly lower serum boron level than controls (P < 0.001). Serum boron level was significantly negatively correlated with RF titer in RA patients (r=-0.22, P= 0.001). No significant correlation was found between serum boron with DAS28, disease functional class, and ESR (P > 0.05). Also, RF titer was a significant predictor of low serum boron level (P= 0.023, OR=-0.07, 95% CI-0.13-(-0.01)). Conclusions: There was a significant low serum boron level in RA patients. RF titer was significant predictor of low serum boron level. This may suggest that boron element may play a role in pathophysiology of RA and its severity. Supplementation with boron element and diets rich in fruits, vegetables, nuts, and pulses may be useful.