Background: Vitamin D is a steroid that has long been implicated in calcium homeostasis and bone mineralization.Aside from its classical roles in healthy individuals, Vitamin D has been shown to exhibit numerous anticancer and immunemodulating properties. In multiple cancers and autoimmune diseases, calcitriol inhibits proliferation, induces apoptosis, decreases angiogenesis, and sensitizes cells to chemotherapy. The aim of this study is to evaluate the level of vitamin D in Egyptian lymphoma patients , as well as to evaluate the value of vitamin D replacement in vitamin Dinsufficient lymphoma patients regarding response to chemotherapy.. Patients and methods:The study was conducted on 100 patients with Diffuse large B cell lymphoma (DLBCL) collected from Internal Medicine Department, Oncology and Hematology Unit at Benha University Hospital during period from February 2020 to May 2022, ptients with established diffuse large B cell lymphoma diagnosed according to WHO guidelines of the 2016 by exicisional or core tissue biopsy. Results: There was Significant relation between the studied groups and disease stage (P = 0.018), KI-67 (P = 0.031), and IPI score (P < 0.001). After treatment, vitamin D revealed an overall significant difference between groups. LDH showed an overall significant difference between the studied groups (P = 0.003). A significant association was reported between the studied groups and complete response (P = 0.03. Those with non responsive disease revealed significantly higher age (52 ±6 years vs. 44 ±11 years, P = 0.047) and male predominance (100% vs 60.2%, P = 0.044). Those with non responsive disease demonstrated significantly higher percentage of high Ki-67 (100% vs. 25.8%, P < 0.001). In addition, a significant association was reported between non responsive and IPI score (P = 0.002. Those with non responsive disease revealed significantly higher LDH (916 ±127 mg/dl vs. 714 ±144 mg/dl, P < 0.001) but significantly lower vitamin D (median = 9 vs. 14, P = 0.007). ROC analysis was done for vitamin D to distinguish those with non responsive disease. It revealed a significant AUC of 0.804 with a 95% confidence interval ranging from 0.656-0.953 (P = 0.007). Conclusion: vitamin D may have a prognostic index & showed asssosiation between it,s deiciency & lymphoma agressivenes also vitamin D replacement might have a role to iprove outcome of treatment.