Abstract : Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disease with unknown etiology. Neutrophil extracellular traps play an important role in SLE pathogenesis and may induce the production of autoantibodies against carbamylated proteins (Anti-carP). To measure serum Anti-carP levels in SLE patients and investigate its role in association with disease activity and severity. The study was conducted on 40 SLE female patients and 40 matched healthy controls. All patients were subjected to full history taking and clinical examination. Disease activity was assessed by SLE disease activity index (SLEDAI), Swollen to tender joint ratio (S/T) used to assess joint activity and disease severity was assessed by Katz score. Serum level of Anti-carP was measured using enzyme-linked immunosorbent assay and correlated with disease activity, severity scores, S/T and hand and wrist ultrasonographic findings. Mean age of patients was 33.78±9.1 years (18-50 years), with a mean disease duration of 6.68±6.02 years (0.17-30 years). Anti-carP serum levels, was significantly higher in patients compared to controls (p <0.001). Regarding disease activity, it was significantly higher in active patients compared to inactive ones (p <0.001). Also, it was higher in patients with high disease severity compared to low disease severity (p <0.001). Serum Anti-carP levels showed significant positive correlation with both SLEDAI and KATZ scores (r=0.726, 0.773 and p <0.001 respectively). However, no relation was found between Anti-carP level and clinical or hand wrist ultrasound findings suggestive for arthritis. Serum Anti-carP showed no association with arthritis in SLE patients in this work. However, increased Anti-carP was associated with high disease activity and severity in patients with clinical manifestations other than arthritis. Anti-carP could be a marker of disease activity and severity in SLE.