Background The anti-neutrophil cytoplasmic antibody (ANCA) renal risk score (ARRS) for predicting renal survival in ANCA-associated vasculitis (AAV) had not previously been validated in adults over 65 years of age and presenting impairments associated with an aging kidney, a high cardiovascular comorbidity burden, and prevalent microscopic polyangiitis. Methods We retrospectively studied a cohort of 192 patients over 65 years of age (median [interquartile range] age: 73 [68; 78]), including 17.2% with renal-limited vasculitis, 49.5% with microscopic polyangiitis and 33.3% with granulomatosis with polyangiitis, at six centres of northern France. The primary study endpoint was the cumulative incidence of end-stage kidney disease (ESKD, maintenance of dialysis for at least 3 months) at 12 months, with death considered as a competing event. Results The median serum creatinine concentration at diagnosis was 300 [202; 502] µmol/L, and 48 (25.0%) patients required dialysis at presentation. The ARRS was high in 43 (22.4%) patients, medium in 106 (55.2%), and low in 43 (22.4%). The cumulative incidence of ESKD at 12 months was 0% in the low-risk group, 13.0% [7.6–20.0] in the medium-risk group, and 44.0% [29.0–58.0] in the high-risk group (p < 0.001). In the subgroup of 149 patients presenting a medium or high score, the ARRS had a C-index of 0.66 [0.58–0.74] for the prediction of ESKD at 12 months; this rose to 0.86 [0.80–0.90] when dialysis status at diagnosis was included. Conclusion The ARRS was a poor predictor of kidney survival at 12 months among patients over 65 years of age with renal AAV involvement—especially in the high ARRS group. The addition of dialysis status at diagnosis as an additional clinical parameter might improve the ARRS's predictive performance.