Obesity and insulin resistance are increasingly common in people with type 1 diabetes and may increase the risk of diabetes-related kidney disease1. Tirzepatide, a glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 receptor agonist, produces substantial weight loss and glycaemic improvement, with emerging evidence of kidney benefit in type 2 diabetes2. Whether these metabolic benefits translate into renal protection in insulin-deficient diabetes remains understudied. We therefore examined the structural and functional renal effects of tirzepatide initiated at diabetes onset or after established diabetes and obesity. Eight-week-old male C57BL/6 mice were assigned to four groups. CON mice remained free of diabetes and received standard chow. In the remaining groups, insulin-deficient diabetes was induced using streptozotocin (55 mg/kg/day for five days), with concurrent obesity promoted by high-fat feeding, creating a model of double diabetes. These mice received saline vehicle (DD), tirzepatide from diabetes onset (DD-eTZP), or tirzepatide after 12 weeks of high-fat feeding (DD-lTZP). Tirzepatide was dose-escalated to 40 nmol/kg and administered subcutaneously three times weekly. Mice were followed for 24 weeks (n=8/group). Kidney weights, serum and urinary analyses, and renal histopathology were assessed at endpoint. Data was analysed using one-way ANOVA with Bonferroni correction and is presented as mean ± SEM. At study end, DD-eTZP and DD-lTZP had reduced body weight versus DD (27.7±0.4 and 26.8±0.5 vs 32.5±0.4 g; both p<0.0001) and lowered blood glucose (10.3±0.4 and 14.2±1.8 vs 31.4±0.9 mmol/L; both p<0.0001). Both regimens reduced kidney-to-body-weight ratios by 22–34% and improved tubular vacuolation, casts and glycogenated nuclei (all p<0.05 versus DD). Only early treatment significantly reduced tubular dilation and urinary albumin-to-creatinine ratio compared with DD (both p<0.05). Tubulointerstitial fibrosis and glomerulosclerosis were unchanged by tirzepatide treatment. Both early and delayed tirzepatide improved glycaemia and attenuated renal injury, with benefits evident even when treatment commenced after established disease.