Background: Systemic lupus erythematosus (SLE) is a systemic autoimmune disease where chronic inflammation and organ damage is observed due to various suspected causes e.g. inadequate levels of vitamin D (a steroid hormone with immunomodulatory effects). Objective: To assess vitamin D (VD) levels in serum of patients with lupus nephritis (LN) in comparison with patients with extra-renal lupus and healthy controls, and to assess the relation between VD levels and the various clinical and laboratory disease parameters. Patients and Methods: This was a case-control study that was held in Zagazig University Hospitals between June 2019 and July 2020. The study included 40 patients admitted with systemic lupus erythematosus (SLE) with and without lupus nephritis (LN), and 20 age-matched healthy subjects. Laboratory investigations such as complete blood count, electrolytes, PTH, acute phase reactant, complements, Ads DNA and 25(OH) D levels of the subjects were measured. Results:  Patients with SLE with lupus nephritis were significantly lower regarding vitamin D with no significant difference between patients with SLE without LN and control group. Conclusions: Our study revealed a high frequency of Vit D deficiency and insufficiency among patients with SLE with LN compared to SLE without LN and healthy controls. Keywords: