Renin-angiotensin system (RAS) blockers, including angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs), are known to slow chronic kidney disease (CKD) progression in patients with established renal impairment. However, whether RAS blockade can prevent new-onset CKD in patients with type 2 diabetes and hypertension who maintain preserved kidney function remains unclear. We addressed this question in a multicenter retrospective cohort study. Beginning with 316,693 individuals with type 2 diabetes and newly diagnosed hypertension, we retained 3,316 ACEI/ARB users and 1,409 nonusers after generalized boosted model weighting to equalize baseline characteristics. Three renal endpoints were followed: a sustained eGFR below 60 mL/min/1.73 m2, incident albuminuria (urinary albumin-to-creatinine ratio of 30 mg/g or higher), and a composite of either. Associations between RAS blocker exposure and each endpoint were quantified using Cox proportional hazards regression, with competing-risk and time-dependent variants applied as confirmatory analyses. ACEI/ARB therapy was associated with a significantly lower risk of new-onset CKD (HR 0.72; 95% CI 0.60-0.86), with consistent findings after accounting for competing risks (HR 0.73; 95% CI 0.61-0.87) and time-dependent exposure (HR 0.81; 95% CI 0.68-0.96). These findings suggest that RAS blockade may confer early kidney protection in patients with type 2 diabetes and hypertension with preserved renal function. People with type 2 diabetes often develop high blood pressure, and together these can slowly damage the kidneys. Medicines known as renin–angiotensin system blockers (angiotensin-converting enzyme inhibitors and angiotensin receptor blockers) are already used once kidney damage is present, but it has been unclear whether they help earlier. Starting from 316,693 people with type 2 diabetes across seven hospitals in Taiwan, we identified those who had normal kidney function and no protein in the urine when blood-pressure treatment was first started, and compared 3,316 who began one of these medicines with 1,409 who began other blood-pressure medicines. Those taking an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker were about 28% less likely to develop new kidney disease, with the clearest benefit in preventing protein from appearing in the urine, an early sign of kidney injury. These medicines may therefore be linked to kidney protection before damage begins, although a randomized trial is still needed to confirm this.KEY MESSAGESWhat is known: Renin–angiotensin system blockers are established therapy for slowing kidney function decline in patients with type 2 diabetes who already have a reduced eGFR or albuminuria, but whether they offer any advantage over other antihypertensive classes before kidney injury has occurred remains uncertain, with prior trials yielding inconsistent results.This study adds: Starting from a multicenter database of 316,693 patients with type 2 diabetes, we compared 3,316 ACEI/ARB users with 1,409 nonusers who had preserved kidney function and normoalbuminuria at the initiation of antihypertensive therapy, and found that ACEI/ARB use was associated with a significantly lower risk of new-onset CKD (HR 0.72; 95% CI 0.60–0.86), with the association most robust for incident albuminuria and the composite endpoint.Potential impact: When antihypertensive therapy is first initiated in patients with type 2 diabetes and preserved kidney function, an ACEI or ARB may be a reasonable preferential choice for the primary prevention of albuminuria and new-onset CKD, a hypothesis that now warrants prospective confirmation.