Background: Chronic rhinosinusitis (CRS) is a sinonasal mucosa inflammation. It's categorised by polyp status. But data implies that chronic rhinosinusitis without nasal polyps (CRSsNP) and CRSwNP are discrete disease entities with distinct inflammatory milieu. The aim of the study: to evaluate the impact of vitamin D supplementation (4000 IU/day) on the risk of nasal polyp recurrence in CRSwNP individuals who have had functional endoscopic sinus surgery (FESS). Methods: This randomized triple-blinded controlled research was performed on thirty cases presented in Outpatient Clinic of Benha University Hospitals with CRS during the study period of 6 months. The study duration was from September 2022 until March 2023. Result: there was a significant variation among the examined groups concerning Six months follow up Meltzer scores, six months follow up SNOT-22 scores and Nasal polyp recurrence. there was no significant distinction among the investigated groups as concern Demographic characteristics, Serum Vit.D level results, Preoperative Meltzer scores and Preoperative SNOT-22 scores. Conclusion: The current investigation demonstrated the effectiveness and safety of vitamin D supplementation in preventing the recurrence of polyposis in individuals with CRSwNP who had endoscopic sinus surgery. This is the first randomized, triple-blind, placebo-controlled research to examine the effects of VD3 on reducing the recurrence rate of nasal polyposis after endoscopic sinus surgery.