Autoantibodies to complement are associated with various diseases. Anti-C1q antibodies are present in all patients with hypocomplementemic urticarial vasculitis, but also with varying prevalence in other conditions. Anti-C1q may interfere with the clearance of apoptotic cells, so influencing induction and expression of autoimmunity. The aim of this work is to study the relation between anti-C1q antibodies and systemic lupus erythematosus (SLE) and its manifestations including renal affection. The presence and levels of anti-C1q antibodies were investigated using enzyme-linked immunosorbent assay technique. The study included 70 Egyptian patients suffering from SLE and 18 healthy controls. They were 65 females and five males. Their age ranged from 12 to 48.5 years with a mean value of 27.4 ± 8.4. Anti-C1q antibodies were statistically significantly elevated in cases compared with controls being positive in 37.2% (mean 18.3 ± 27.1) in patients versus 11.1% (mean value 4.1 ± 3.5) in controls (P = 0. 03). Anti-C1q antibody-positive patients (n = 226) had significantly higher SLE Disease Activity Index (SLEDAI) (16.1 ± 9.9) compared to negative patients (n = 44) (SLEDAI = 8.1 ± 7.7) P = 0.000. Regarding renal affection, the presence of anti-C1q-positive antibodies was associated with proteinuria, P = 0.002. In conclusion, anti-C1q was more common in patients with SLE and disease activity. We confirmed a significant association of anti-C1q with renal involvement, independent of demographics and other serologies.