The study designed to investigates the anatomical and histological structures of the thymus gland in broiler chick embryos.  Ten healthy, normal embryos at 12^th and 20^th days old chick embryos was used, divided into five embryos for each age. The thymus was well developed at 12^th day chick embryo, Anatomically consisted of 6-8 lobes which are similar in both sides .small, translucent bean shaped lobes that became pale in color at 20^th day old embryo, these lobes located in both sides of the neck, positioned parallel to the jugular vein and vagus nerve.  
            Histological structures of thymus gland were composed of capsule, cortex and medulla.  At 12^th day old of chick embryo the thymus was surrounded by a thin connective tissue capsule, which septa extends into the gland stroma to form a lobulation for each lobe, the cortex and medulla was not differentiated at this age. At 20^th day old chicks embryo, the lobules start to recognize and composed of external dark stained cortex with a high population of lymphocytes and internal light stained medulla with less abundant of lymphocytes , reticular fiber and epithelial reticular cells with the appearance of Hassall's corpuscles.