Background: Serological markers for lupus nephritis (LN) have recently been established in Systemic Lupus Erythematosus (SLE) cases with high levels of anti-C1q antibodies (SLE). We investigated serum level ofanti-C1q antibodies in Egyptian female SLE cases less than 25 years to detect if they could serve as a biomarker for nephritis activity. Methodology: This hospital based case control study was conducted on 180 female subjects from Sept 2021 to March 2022. Patients were collected from rheumatology, nephrology and pediatrics departments of Alhusien and Bab Alsharia University hospitals, all female cases underwent follow-up. Their ages were less than 25 years old. They were divided into three groups. Group 1 included 60 female cases of SLE and active lupus nephritis. Group 2 included 60 female cases of SLE without active lupus nephritis. Group 3included 60age matched apparently healthy females as a control group. Results: There was significant elevation in ESR and anti C1q in group 1 more than other two groups with decrease in C3,4. In group 1 Anti-C1q was significantly correlated with 24 h Protein, C3&4 and SLEDAI Score. In group 2 Anti C1q was significantly correlated with C3 only. ESR, C3, C4, Anti-C1q, ANA Titer and Anti dsDNA were considerable sensitive as positive markers for lupus nephritis in SLE cases. Conclusion: Proteinuria, complement levels, and renal SLEDAI all correlate with renal disease activity and flare-ups, as do anti-Clq auto antibodies. Anti-C1q antibodies, instead of other validated disease activity markers, may be utilized to diagnose nephritis flare in pediatric and adolescent Egyptian females with SLE.