Qualitative determination of chemical and nutritional composition of Cassia occidentalis, an underexploited crop seed in Nigeria, was carried out. Seeds of C. occidentalis were found to be rich in crude protein, carbohydrate, and mineral elements. Mineral analysis of C. occidentalis showed the seed as good source of antioxidant micronutrients such as iron, calcium, potassium, sodium and magnessium. The phytochemical screening of the seed showed the presence of carbohydrate, terpene, steroid, sugar and tannins. Alkaloids, saponnins and glycosides were absent. Although the oil has a very low peroxide value and high iodine value, it cannot be recommended for consumption because of the low yield as well as its repulsive odour. The seed, however, can serve as a cheap source of protein, energy, as well as antioxidant micronutrients supplements in both man and animal.