Researchers have developed and validated an individualized prognostic nomogram to estimate the risk of renal function decline in children with IgA vasculitis nephritis (IgAVN). The study included 603 children with biopsy-confirmed IgAVN and a follow-up of at least 12 months, with the cohort divided into a training (80%) and validation (20%) set. The primary endpoint was a decline in eGFR below 90 mL/min/1.73 m² or ≥30% from baseline at 12 months. During a median follow-up of 48.7 months (IQR 28.5–73.3), 68 children (11.3%) reached this point. The model identified five predictors: male gender (HR=2.12), renal IgA deposit 3+ (HR=2.66), ISKDC grade IV–VI (HR=4.63), Oxford T1/2 lesions (HR=4.72), and baseline serum creatinine. The nomogram showed good discrimination (C-index=0.796; AUC 60 months=0.859; 84 months=0.850), calibration and clinical benefit. Kaplan-Meier analysis confirmed a higher risk in the high-risk group (log-rank p<0.001). The tool enables personalized decisions shortly after the biopsy.