This study aimed to investigate the development of the kidneys and adrenal glands in rabbits using histological, histochemical, and biochemical techniques. The experiment was conducted on 28 kidney and adrenal gland samples at different ages (one day, seven days, fourteen days, and ninety days). Histological findings revealed that the kidney was covered by a small amount of collagen and reticular fibers and had a thin capsule that thickened with age. The renal corpuscle increased in diameter as the age progressed. The proximal convoluted tubules were the longest, surrounded by cuboidal epithelial tissue, and had a brush border. The adrenal glands were encased in a well-developed capsule, and the cortex was divided into the glomerular, fasciculate, and reticular zones. The medulla was composed of large, pale-staining hexagonal cells arranged in small anastomosing strands held together by reticular fibers and separated by sinusoids. Norepinephrine cells were smaller. Histochemical studies showed that the brush border in the kidney responded positively to PAS, AB, and PAS-AB stains. PAS staining revealed that the basement membranes of the glomerulus and renal tubules were fully developed. Biochemical tests showed significant age-related differences in uric acid levels and each enzyme. As the urea burden increased, more urine was needed because the kidneys' ability to filter urea was limited. The kidneys underwent postnatal developmental changes, reaching maturity three months after birth when the normal adult nephron structure was observed. This indicated that the structure of the kidney and adrenal glands developed after birth with age progression.