Background: Lupus nephritis (LN) affects 50% of systemic lupus erythematosus (SLE). LN often leads to renal failure. Thus, early diagnosis of LN is mandatory for the prevention of complications. Objective: We aimed to evaluate serum and relative omentin mRNA gene expression levels as a noninvasive diagnostic test of LN and to assess their correlations with disease activity, clinical and laboratory features of SLE. Patients and Methods: Case-control study included 104 subjects, 60 patients with SLE were stratified into two subgroups LN group (n=25) and the non-LN group (n=35). Disease activity was assessed by the SLE disease activity index (SLEDAI). Measurement of serum omentin was done by ELISA and investigation of omentin mRNA relative expression was done by real-time PCR. Results: Our results detected that serum omentin levels were significantly lower in the LN group and non-LN group compared to controls. Intriguingly, omentin mRNA relative expression levels were significantly lower in the LN group and non-LN group compared to controls. Among the LN group, there were significant negative correlations between serum and relative omentin mRNA expression with SLEDAI, clinical, and laboratory features of LN. Moreover, SLEDAI, proteinuria, and serum creatinine were independently correlated with them. The sensitivities and the specificities of serum omentin were 91% and 65.5% respectively. While the relative omentin mRNA expression diagnostic power showed sensitivities and specificities of 93% and 68.8% respectively. Conclusion: LN group had significantly lower values of serum and relative omentin mRNA expression compared to non-LN and control groups. Additionally, it was negatively correlated with SLEDAI, clinical and laboratory features of LN. Thus, they could be used as non-invasive predictive markers of LN.