Proximate composition, amino acid, mineral content, vitamin composition and anti-nutritional factors of Cassia occidentalis seed were determined using a standard method of analysis. The result showed that the seed had the following proximate composition on dry weight (DW) bases: ash (39.00%), moisture content (2.00%), crude protein (18.50%), crude lipid (7.55%, Crude fibre (16.30%) and carbohydrate (16.75%). Six amino acid was detected (isoleucine, leucine, tyrosine, alanine, glutamine and valine) indicating that the seed is a good source of amino acid for adult. Vitamin composition (beta- carotene, thiamin, riboflavin, niacin, ascorbic acid and alpha-tocopherol) were also detected in the seed. The anti-nutrient analysis showed that the seed contains total phytate (1.25 mg/100 g) oxalate (1.70 mg/100 g) and nitrate (0.82 mg/100 g). While hydrogen cyanide was not detected. Elementary analysis revealed that the seed contain Na (0.015±0.02 mg/100 g), Cu (0.028±0.04 mg/100 g), Zn (0.441±0.10 mg/100 g), Mg (2.003±0.30 mg/100 g) and Mn (0.041±0.03 mg/100 g) while Cd, Cr and Pb were not detected. Comparing the nutrients and anti-nutrient constituent with WHO and FAO values, the result indicated that the Cassia occidentalis seed had the potential to be used as a source of nutrient in alleviating macro and micronutrient deficiencies.