Obesity is a global health issue of great concern. It leads to hyperplasia, hypertrophy of adipocytes, and metabolic complications including coronary artery disease, and cerebrovascular disease. The effectiveness of cinnamon zeylanicum as a medicinal herb comes from its anti-inflammatory and antioxidant properties. The purpose of this study was to assess the potential beneficial effects of cinnamon on adrenal toxicity caused by a high-fat diet in male albino rats. Four equal groups of the experimental animals were used, the control group, the cinnamon group, the high-fat diet group, the high-fat diet, and the cinnamon group. Animals fed cinnamon showed similar results with the control group. The adrenal cortex sections of high-fat diet-fed animals showed different degenerative changes in all layers of the adrenal gland, cortex, medulla, and corrugation of the capsule. Ultra structurally, a lot of adrenal cortical cells appeared with irregular pyknotic nuclei, swollen mitochondria, dilated sER, and numerous lipid droplets with variable shapes and sizes. Moreover, a significant rise in the immunohistochemical expression of cytochrome c in a large number of cortical cells was observed. On the contrary, animals given cinnamon and a high-fat diet exhibited noticeable improvement in the structure of the adrenal gland, and the immunohistochemical expression of cytochrome c was observed in the third group. The histological structure of the adrenal gland appeared to be mostly the same as the control one. Cinnamon has a potential effect in improving adrenal toxicity against a high-fat diet because of the natural constituent capable of its pharmaceutical effects.