A 12-year-old, spayed, diabetic, domestic shorthair cat (body weight: 3.0 kg) with hypertension and kidney disease was treated with the antihypertensive agents carvedilol and telmisartan. Carvedilol monotherapy was started on Day 11, and concomitant administration of telmisartan was started on Day 294. Recombinant human insulin was initially administered at 1.2–1.5 IU/kg, but this dose was successfully reduced by 0.6 IU/kg with blood glucose stability on Day 375. Antihypertensive effects were also observed, but kidney disease worsened, and urinary β2-microglobulin was detected as a biomarker of kidney disease. We report a case of increased insulin sensitivity and stable blood glucose with telmisartan and carvedilol in a diabetic cat with hypertension and kidney disease.