Tribulus terrestris has been commonly used in folk medicine to energize, vitalize and improve sexual function and physical performance in men and laboratory rats. To study the effect of Tribulus terrestris on the number of Leydig cells. Tribulus terrestris was given to mature male rats as an oral single herbal suspension in a dose of 2.0mg /1000gbody weight for 14 days to stimulate spermatogenesis. Formalin fixed paraffin-embedded tissue sections were performed for histological, immunohistochemical and morphometrical studies. Histological study revealed wider seminiferous tubules and increased spermatocytes population with an increased sperm density inside the lumen of the tubules. Morphometrically, the diameters of seminiferous tubules and thickness of the germinal epithelia were significantly increased in Tribulus terrestris treated rats than that of the control group. There was no significant difference between the number of Leydig cells in the control and experimental groups. The activity of Leydig cells, manifested by the increments in the diameters, thickness of germinal epithelia and the density of the sperms inside seminiferous tubules, was increased but their number remain unaffected in spite of using the aphrodisiac agent, Tribulus terrestris