Lead is one of the persistent agents found extensively in the environment and has destructive impacts on the tissues. Regarding the high spread of lead, particularly in Iran, we investigated the effects of lead acetate II on the expression level of osteocalcin gene and histological changes of bone. 40 chickens were randomly divided into four groups. As well as the libitum, the control group was fed with distilled water, while treatment 1, 2, and 3 groups were fed with distilled water and 50, 100, and 200 ppm of lead acetate II, respectively. Alterations in the histological profile of bone including decreased level of bone and pyknosis in the nuclei of osteocytes, and decreased expression of osteocalcin gene are the results of exposing to the lead. Regarding the adverse effects of lead on the bone, the spread of this toxic metal must be limited to decrease its adverse impacts on the birds, especially chickens.