Background: Deficiencies in anti-C1q antibodies were substantially linked to the development of lupus nephritis. Objective: To investigate the diagnostic value of serum anti-C1q auto antibodies used as a reliable marker for diagnosis of lupus nephritis in children. Patients and Methods: at Zagazig University Children's Hospitalseventy-two child included in the study were classified into 3 groups: Group (A): 18 children diagnosed with lupus nephritis flare at time of study. Group (B): 18 children diagnosed with lupus nephritis quiescence stage at time of study, and Group (C): 36 healthy children. Serum anti-C1q autoantibodies was assessed in all participants. Results: Anti C1q at cutoff point 35 in Group (A) 15 (83.3%) had anti C1q value more than or equal 35.1 (5.56%) had anti C1q value between 9 – 35 and 2 (11.1%) had anti C1q value less than 9 while in Group (B) 14 (77.8%) had anti C1q value between 9 – 35 and 4 (22.3%) had anti C1q value less than 9 and in group (C) all children had anti C1q value less than 9. Lupus nephritis had a superior positive prognostic marker in the form of anti-C1Q, which had a sensitivities of 100 and specificities of 81.82. Lupus nephritis activity was associated with anti-C1q antibodies, suggesting that they could be beneficial in forming predictions regarding the disease and in assessing its activity. Conclusion: Anti-C1q antibodies can be considered a reliable, sensitive, and specific biomarker for the diagnosis of nephritis flares in pediatric and Egyptian SLE patients, in addition to and possibly replacing other proven disease activity indices.