Background <p>Renal artery stenting is a key treatment solitary-kidney patients. In these high-risk populations, even moderate stenosis can be relevant, making timely revascularization crucial. Despite this, long-term evidence dedicated to these groups remains limited.</p> Purpose <p>To evaluate long-term outcomes and predictors of renal artery stenting in solitary-kidney patients, and to compare results between transplanted and non-transplanted recipients.</p> Materials and methods <p>This retrospective single-center study included 40 patients treated from 2009 to 2024. Inclusion criteria were stenosis ≥ 70% or 50–69% with invasive functional confirmation and ≥ 12 months of follow-up. Outcomes included technical success, clinical success, primary patency, renal function, blood pressure, antihypertensive burden, and dialysis status. Subgroup analyses and multivariate regressions were performed.</p> Results <p>Technical success was 100%, with no major complications, and clinical success was 92.5%. Primary patency at 1, 2, and 3 years was 95%, 92.5%, and 87.5% (<i>p</i> = 0.20). Renal function improved significantly (eGFR + 11.5 mL/min, <i>p</i> = 0.0008). Transplant recipients showed a greater eGFR improvement (+ 14.9 vs. + 7.1 mL/min), although not statistically significant. Renal function remained stable at long-term follow-up (<i>p</i> = 0.213). Atherosclerotic nephropathy and dyslipidemia predicted smaller creatinine improvement (β = 0.37; <i>p</i> = 0.03). Functional solitary-kidney status predicted greater systolic pressure reduction (β = −0.44; <i>p</i> = 0.01). Absence of peripheral artery disease and lower baseline blood pressure predicted ≥ 3-year patency (OR = 2.7; <i>p</i> = 0.02). Baseline creatinine &gt; 3&#xa0;mg/dL predicted persistent dialysis (OR = 3.4; <i>p</i> = 0.01).</p> Conclusion <p>Renal artery stenting is safe, durable, and effective, with subgroup-specific factors influencing long-term outcomes.</p>