INTRODUCTION: Infertility is common among couples of child-bearing age and approximately half of known causes of primary infertility are attributable to male factor. It is still unclear whether the injurious effects of cigarette smoking on sperm characteristics and infertility are due to nicotine. Therefore, the present study investtigated the effects of orally administered of nicotine on sperm characteristics and libido in adult male albino rats. The study also sought nicotine effects on fertility rate, litter size and weight in female animals cohabited with nicotine treated male rats. METHODS: Forty male and twenty-five female rats were used for the study. The male rats were divided into five groups and were treated for a period of 30 days with nicotine 0.5 mg/kg (low dose) and 1.0 mg/kg (high dose) per body weight while the control rats received 0.2 ml/kg normal saline. The fourth and fifth groups were gavaged with 0.5 mg/kg and 1.0 mg/kg body weight of nicotine but were left untreated for another 30 days. These groups served as the recovery groups. At the end of each experimental period, sperm analysis, fertility study, litter weight and size were determined. RESULTS: Sperm motility and count significantly decreased (P < 0.05) while the percentage of abnormality significantly increased (P < 0.05) in both treatment groups. However, there was an insignificant decrease (P > 0.05) in the viability and semen volume of the treated groups. Fertility studies revealed that nicotine reduced libido in male rats, litter weight and number delivered by the untreated female during the experiments. CONCLUSION: The present study showed that nicotine has a dose-dependent deleterious effect on the sperm characteristics and that fertility is ameliorated by nicotine cessation in male rats.