The work estimates histological changes in the myocardial structure of old, hypertensive rats after the introduction of cryopreserved cord-blood nucleated cells (CBNCs). The goal of the work was to estimate the structural organization of myocardial tissues and blood vessels on the third, seventh, and 30th days after the intraperitoneal administration of cryopreserved CBNCs to rats with stress-induced arterial hypertension. The experiments were carried out on 28- to 30-month-old, white, outbred, male rats. It was established that the introduction of cryopreserved CBNCs to old animals with stress-induced arterial hypertension led to a significant improvement in the structure of myocardial tissues and blood vessels. The number and area of cardiomyocyte nuclei increased already on the third day, and these changes were accompanied by a pronounced neoangiogenesis. The density of fibroblasts in the interstitial connective tissue and around the blood vessels increased by the 30th day after the introduction of cryopreserved CBNCs. There was a decrease in perivascular and interstitial edema, and there were no traits of focal ischemia and cardiosclerosis in the tissues.