Systemic lupus erythematosus (SLE) is an autoimmune disease in which the complement system plays a role in its pathogenesis. Mannose-binding lectin (MBL) is a serum protein, being a component of innate immune system, it is responsible for lectin pathway of complement activation. The presence of several polymorphisms at the coding regions of the MBL-2 gene, especially single point mutation at codon 54, leads to decreased level and /or functional deficits of MBL, which seems to be a risk factor for occurrence of autoimmune diseases, such as in SLE. So, this study was carried out to determine the role of the serum MBL concentration and the genetic polymorphisms of MBL-2 gene exon 1 codon 54 in Egyptian patients with SLE. Forty-eight SLE patients and 48 matched healthy controls were investigated. MBL serum level was measured by ELISA technique. MBL-2 polymorphism at exon 1 codon 54 was determined by PCR-RFLP. Our results revealed a significant reduction in MBL serum level among SLE patient group in comparison to the control group (P<0.001). MBL-2 genotyping among SLE patients, revealed the wild type (A/A) in 52.1% and mutant types (A/B, B/B) in 47.9%. While among healthy controls, the wild type was detected in 81.2% and the mutant types in 18.8% with a statistically significant association between this polymorphism and SLE susceptibility (P=0.008). Comparison of MBL serum level among different genotypes within the patient group showed that the mutant allele had a suppressive effect on MBL serum level. In conclusion, carrying MBL-2 exon-1 codon 54 variant allele B was shown to be a risk factor for SLE.