Mucuna urens is a shrub from the family of Fabaceae. It is claimed by the local people in Akwa Ibom State, Nigeria to weaken the penis and reduce sexual performance in men. This work was designed to study the effects of methanol extract of Mucuna urens on the sexual behaviour and sperm parameters of male albino rats. For the sexual behaviour experiment, 30 sexually mature male rats were used weighing (130-188 g). Animals were divided into 5 groups of 6 animals each. Group 1 received 5 mg/kg of tween 80, groups II, III and IV received the low dose (500 mg/kg), middle dose (1000 mg/kg) and high dose (1500 mg/kg) of the extract respectively while group V received 1 mg/kg of testosterone for seven days. Females used for the experiment received 17- β estradiol (8 g/kg body weight) and progesterone (500 g/kg body weight) 48 hours and 4 hours respectively prior to the experiment. For the sperm analysis, 30 male albino rats weighing (130 -176 g) were used. Animals were divided into 5 groups of 6 animals each. The first group received 5 mg/kg of tween 80, groups II, III and IV received low dose (500 mg/kg), middle dose (1000 mg/kg) and high dose (1500 mg/kg) of the extract respectively for 14 days. Group V received 1 mg/kg of testosterone twice weekly. Animals were sacrificed and the sperm was analysed. The extract altered significantly some of the parameters of sexual behaviour which include an increase in mount latency and a decrease in intromission latency when compared to the negative control and positive control group. There was a dose dependent decrease in mount frequency and intromission latency. There was a decrease in the post ejaculatory interval of the extract group compared to the negative control and positive control group. There was a distortion in sperm morphology resulting in sperms with curved and bent necks and sperms with a slender body. The observed effects may in part be due to the presence of the different phytochemical constituents in the seed.