The aim of this study was to investigate the toxicological effect of the methanol extract of the seeds of Napoleona imperialison some biochemical parameters of rats. From the studies, the phytochemical analysis of N. imperialis seed extract showed the presence of phenols, flavonoids, carotenoids, carbohydrates, saponins, alkaloids, hydrogen cyanide, phytates, tannins and oxalates, while the quantitative phytochemical constituents of the seed methanol extracts constitutes; phenols (0.81mg/g), flavonoids (0.79mg/g), carotenoids (1.25mg/g), carbohydrates (0.99mg/g), saponins (1.99mg/g), alkaloids (0.56mg/g), HCN (18.74mg/g), phytates (1.56mg/g), tannins (1.35mg/g), and oxalates (0.85mg/g).The acute toxicity test of the methanolic extract showed no toxicity up to 2900mg/kg body weight but proved to be toxic at 5000mg/kg body weight of the seed extract. Napoleona imperialis seed extract were administered orally for twenty eight days. On day 29, after an overnight fast, blood samples were collected from ocular vein for biochemical analyses after which the animals were sacrificed. Effect of the extract on different biochemical parameters such as, serum triacylglycerol, serum cholesterol, HDL, LDL, T. bilirubin, AST, ALT, ALP, creatinine, blood urea, potassium, MDA, SOD, GSH, GPx, catalase were measured utilizing standard methods. Napoleona imperialis leaf extract at the doses of 100mg/kg, 200mg/kg, 400mg/kg and 600mg/kg body weight were given orally every morning during treatment to show the effect of dose concentration. The triacylglycerol (TAG) concentration was found to be significantly (p<0.05) higher in group 4 and 5 rats administered 400 and 600 mg/kg b.w. of the extract respectively compared to the TAG concentration of normal control rats (group 1). Significant (p<0.05) elevation was observed in the total cholesterol concentration of group 4 rats (400mg/kg b.w. of extract) compared to the normal control.AST activity was found to be non-significantly (p>0.05) higher in all groups. ALT activity for all groups showed no significant (p>0.05) difference. ALP activity was found to be significantly (p<0.05) increased in all the groups compared with normal control. There was no significant (p>0.05) difference in MDA Concentration and GPx and GSH activities in all groups compared to group 1. SOD activity increased non-significantly (p>0.05) when compared to group 1(normal control). Catalase activity was observed to be non-significantly (p>0.05) elevated in group 2, 4 and 5 rats compared to the normal control rats (group 1). On the other hand, there was a significant (p<0.05) increase in group 3 rats. No significant (p>0.05) difference were seen in both potassium and total bilirubin concentration. Urea concentration of all groups on comparison with the normal control rats was observed to be significantly (p<0.05) higher. There was a non-significant (p>0.05) increase in creatinine concentration for all the groups when compared to normal control. The histomorphological changes in the liver, kidney and testes sections of the different groups of rats (untreated/normal control and treated/600mg/kg b.w. of methanol extract of Napoleona imperialis seeds) were absent. Further studies are necessary to investigate methods to detoxify the toxic principles in Napoleona imperialis seed for safer consumption for both humans and animals.