BACKGROUND: Hypertrophic scars and keloids are human cutaneous fibroproliferative conditions that develop after burns, trauma, surgery, and inflammation. Vitamin D inhibits keloid fibroblast proliferation by reducing TGF-β-induced extracellular matrix formation, boosting matrix metalloproteinase activity, and reducing inflammation. AIM: To study the effect of intralesional and systemic Vitamin D3 injection on hypertrophic scars and keloids and whether vitamin D3 deficiency increases scarring. PATIENTS AND METHODS: This study included 30 hypertrophic scars and keloid patients divided into groups depending on serum vitamin D levels. Every patient was tested for vitamin D using ELISA. Group I: patients with vitamin D deficiency or insufficiency received a systemic injection of vitamin D (cholecalciferol 200 000 I.U.) once monthly for 3 months with a calcium oral supplement and intralesional vitamin D injections on hypertrophic scars and keloids. Group II: patients with sufficient vitamin D received only intralesional vitamin D injections. RESULTS: Vitamin D deficiency did not affect scar formation or severity (total Vancouver scar scale before assessment) with a p value > 0.05. All instances showed a substantial drop in vascularity, pliability, and total Vancouver scale score (p value < 0.05) following intervention, but no change in scar pigmentation or height. Scar assessment following intervention did not significantly differ between research groups (p > 0.05). CONCLUSION: Injection of vitamin on hypertrophic scars and keloids enhances vascularity and pliability in patients with sufficient serum vitamin D levels and those with deficient or insufficient serum vitamin D levels after improving them by systemic injection of vitamin D without any effect on height and pigmentation of scars. TRIAL REGISTRATION: NCT06301178.