Blood calcium level can be controlled by the action of parathyroid gland on the bone via parathyroid hormone that responsible for bone mineralization. The study aimed to demonstrate the developmental histological structure of parathyroid gland and bone from one day after birth to twenty four month. Forty-five male Guinea pigs, immature and mature were used for this study. Samples were taken from parathyroid gland and bone and processed for histological examination. Parathyroid gland formed of fibrous capsule and fine septa extending to cellular parenchyma which contained both chief and oxyphil cells. From age of 1 day to 17 month, only chief cells with no differentiation were present in parathyroid gland. Chief cells cytoplasm might be granular, vacuolated or empty according to secretory activity of cells. At 18 month, oxyphil cells started to appear however, chief cells were differentiated into dark and light cells at 24 months. Compact bone was characterized by regular bone lamellae around vascular Haversian vessels that penetrated the bone instead of Haversian canals in Guinea pig. At early life, bone was not completely ossified forming from hyaline cartilage and spongy bone. Vertebrae were completely ossified at 4 month of age and consisted of spongy bone. At 2 weeks and 1 month, femur and ribs were completely ossified consisting of compact bone.