The oxidative-antioxidative status is closely associated with the progression of systemic lupus erythematosus (SLE), and oxidative stress is customarily found in patients with SLE. N-acetylcysteine (NAC), a typical antioxidant, is reliable and often applied for clinical treatment. Lupus nephritis (LN) is a kidney disorder associated with SLE, but the treatment of LN with antioxidants is rarely documented. The present report describes two cases of early-stage LN that were orally treated with 1,200 mg NAC in addition to the standard therapy with hydroxychloroquine and calcitriol. Following the NAC administration, the glutathione level largely increased while the level of the lipid peroxidation biomarker 8-iso-prostaglandin F2α declined in both cases. In addition, the routine blood counts, 24-h urine protein, erythrocyte sedimentation rate and the SLE disease activity index were markedly improved. In conclusion, the present report of two cases has shown that NAC, as an antioxidant, may exert a beneficial effect to modulate the oxidative status in LN; however, the underlying mechanisms require further investigation.