The study aimed to investigate the role of anti-C1q antibodies in patients with systemic lupus erythematosus with kidney damage. Methods: A prospective, cross-sectional study on 42 patients diagnosed with systemic lupus erythematosus according to SLICC 2012 criteria, treated at the Center for Allergy - Clinical Immunology, Bach Mai Hospital from July 2021 to October 2022. Results: The rate of positive anti-C1q antibodies in patients with systemic lupus erythematosus with kidney damage was 54.8%. The mean duration of disease was 1.06 ± 2.22 years, the positive group had a shorter disease duration than the negative group. In the positive group, the most common symptom was edema (63.2%), polymembrane effusion (57.7%), vasculitis (33.3%), clinical renal failure (61.1%), of which urinary less than 40%, the image of chronic kidney disease on ultrasound accounts for 36.4%. There was no difference in histopathology on renal biopsies between the 2 groups. The positive group had lower albumin, urea, and creatinine concentrations than the negative group. Concentration of cross-sectional proteinuria, cross-sectional erythrocytosis, 24-hour proteinuria was higher in the positive group than in the negative group, in which, in the positive group, 24-hour proteinuria reached the nephrotic threshold (4.90 ± 7.44). The positive group had decreased C3 complement concentration (0.44 ± 0.29), increased anti-DsDNA antibody (109.71 ± 41.53), higher SLEDAI score than the negative group. There was no difference in C4 complement concentration between the 2 groups of patients. Conclusions: In patients with systemic lupus erythematosus, anti-C1q antibodies are strongly associated with kidney damage and disease activity.