The use of nicotine through smoking remains a serious health problem. It has been associated with reduced fertility (Oyeyipo et al, 2011), although the mechanism responsible is still unclear. The present study was to investigate the effects of nicotine administration on sperm function and testicular oxidant and antioxidant system in male albino rats. Twenty four male rats weighing between 200-250g (8-10 weeks) were divided into three groups and treated orally for thirty days. Group I, which served as the control received 0.2ml / kg normal saline, Groups II and III received 0.5mg/kg (low dose) and 1.0mg/kg (High dose) body weight of nicotine respectively. At the end of the experimental period, animals were anaesthetized with 1.9% ether and the testis and caudal epididymis were removed. Sperm analysis was done on the sperm collected from the epididymis while the testis was homogenized for lipid peroxidation and anti-oxidant enzyme assays. Values were expressed as mean ± S.E.M compared by ANOVA. Results showed that nicotine administration significantly (p<0.05) decreased sperm motility (60.2 ±3.96; 40.7 ± 4.63) and count (63.2 ± 5.62; 54.7 ± 6.2) when compared with the control group (94.4 ± 3.60; 107.5 ± 6.8) respectively. There was a significant decrease (p<0.05) in testicular glutathione peroxidase (1910.4 ±53.8 IU/ml), testicular glutathione reductase (1071.0 ±57.1 IU /ml) and superoxide dismutase (1.4 ±0.1 IU/ml) in the high dose group when compared with the control (2489.8±60.1; 1487.6 ±55.0. and 1.9± 0.1 IU /ml) respectively. MDA was significantly (p<0.05) increased in nicotine treated groups (25.4±1.8 µmol/L) and (30.8±1.7 µmol/L) when compared with the control (17.9 ±1.5 µmol/L). These findings suggest that nicotine administration is associated with decreased sperm function, testicular antioxidant and increase testicular lipid peroxidation which results in oxidative damage thereby causing adverse effects on sperm cells.