Vitamin D (VD) plays a significant immunomodulatory role in various autoimmune diseases, including systemic vasculitides. This short review evaluates the existing literature on VD supplementation (VDS) in systemic vasculitis. A systematic search identified two studies focusing on Kawasaki disease (KD) and Henoch-Schönlein purpura (HSP). Both studies suggest potential benefits of VDS in reducing disease onset and recurrence, as well as modulating immune responses. Although current evidence is limited, findings support further investigation into VD as an adjunctive therapeutic strategy in vasculitis.