The present study was designed to investigate the effects of extract of Tribulus terrestris on fertility of Ratus norvegicus. Rats were divided into three groups of 10 rats. (group1: control, group 2 and 3: experimental). Group 2 was given Tribulus Terrestris water extract as an oral drinking at a dose of 2 ml daily for 30 days, while group 3 was fed on alcoholic extract mixed with food. (75g / Kg food weight) daily. After 4 week rats were weighed and their gonads were removed, weighed and processed histological. Data collected were assessed using ANOVA single factor. Tribulus terrestris extract showed statistically significant increase in body weight p<0.05) and testes weight ((p<0.05). Increase in the weight of testes. No effect was detected in females treated with the both Tribulus terrestris extracts. Histological slides of the testes showed a significant increase in seminiferous tubules. And increment in testosterone concentration.