Effects of alcoholic seed extract of Abrus precatorius Linn. were investigated at a dose of 100 mg/Kg body wt./day/rat for 60 days on fertility, semen profile and sperm metabolism of orally administered sexually mature male albino rats using WHO protocols. Serum testosterone levels were also measured using RIA technique. The data revealed that the cauda epididymal sperm motility was significantly lowered with no effect in its sperm concentration by 60 days of feeding. The scanning electron microscopic study on sperm morphology exhibited decapitation, acrosomal damage and formation of bulges on midpiece region of sperms in treated rats. The biochemical studies on epididymal spermatozoa indicated alterations in their energy and/or oxidative metabolism as evidenced by a fall in succinate dehydrogenase and ATPase levels by extract allocation. It did not exert any effect in body and organ weights. But an average number of implantation sites in females after mating with the treated male rats markedly declined. Contrarily, a significant increase in serum testosterone levels was noted by 60 days of administration. Thus, the decrease in fertility rate in extract receiving animals is correlated with reduced sperm motility, metabolism and altered sperm morphology in epididymis.