Thevetia Neriifolia was analyzed for fatty acid composition by using Gas Chromatography (GC) and Gas Chromatography-Mass Spectrophotometer (GC-MS). The oil consist of 97.583% fatty acid of which the most abundant is the monounsaturated (C₁₈H₃₄O₂) Oleic acid (52%), and the others are saturated fatty acids (C₁₈H₃₆O₂) Stearic acid (25%) and the other Palmitic acid (C₁₆H₃₂O₂). The physicochemical studies of the seed oil showed: acid value of 0.515 ± 0.27 mg KOH/g; 117.125±2.38 saponification value and 74.145 ± 0.784 iodine value. Growth performance in albino rats following a feeding period of 6 weeks, using 5%, 10% and 15% of the seed oil compounded feed showed a significant decrease in body weight gain and feed intake in 10% and 15% oil-based feed group relative to control. Enzymatic antioxidant, biomarkers of kidney/liver toxicity and lipid profile of visceral organs were evaluated.