: Systemic lupus erythematosus (SLE) is a chronic multi-system inflammatory connective tissue disorder, affecting kidneys in about 50% of patients. The laboratory tools used to determine kidney affection are modest and relatively inaccurate in their ability to detect SLE activity and lupus nephritis flare. Therefore, new biomarkers for proper detection of SLE activity and lupus renal disease have to be searched. To investigate serum adiponectin as a marker of SLE activity and lupus nephritis. 90 participants were involved and classified into 4 main groups; group I included 36 healthy volunteers as control group, group II included 18 patients with active SLE with lupus nephritis, group III included 18 patients with active SLE without lupus nephritis and group IV included 18 patients with inactive SLE. All participants were submitted to; urine analysis, complete blood count, fasting blood glucose, serum creatinine, liver function tests, serum complement 3 and 4, antinuclear antibody, anti-double stranded DNA level and serum adiponectin levels assays. Serum adiponectin levels were significantly higher in lupus nephritis group than in the other two SLE groups and controls. Adiponectin at a level >2.9μg/mL had a greater sensitivity 92.5% and specificity 98.3% for identifying SLE activity than both C 3 at a level < 44.4mg/dl with sensitivity 73.4% and specificity 75.6% and C4 at a level < 10.4mg/dl with sensitivity 65.2% and specificity 68.4%. Serum adiponectin could be used as an early marker for identifying SLE activity and lupus nephritis.