The vitamin composition, protein quality and mineral bioavailability of matured stems of Opuntia dillenii were investigated. The sample was analyzed using an automatic amino acid analyzer (JEOL (JLC 500/V) for the assessment of amino acids, and an atomic absorption spectrophotometer for the mineral composition analysis while the vitamin composition was evaluated using spectrophotometric methods. The amino acid composition ranged between 1.31g-20.08g/100g. Arginine and leucine had the highest concentration of essential amino acids while glutamate and aspartate were the most abundant non-essential amino acid in the studied plant. The percentage Total essential amino acids (with Histidine), Total non-essential amino acids, Total aromatic amino acids, and Total sulphur amino acids were 41.8%, 56.1%, 8.1% and 5.3% respectively. The results for the protein quality indices:-the predicted protein efficiency ratios (P-PERs I, II, and III) were 2.45, 2.59 and 3.49 respectively. The amino acid scoring pattern showed valine and lysine as the limiting essential amino acids considering the requirements of preschool children. The vitamin analysis showed that vitamin B 12 and vitamin A were the most occurring vitamins. The mineral analysis results revealed magnesium, calcium and phosphorus as the most concentrated while the [phytate]/ [calcium] ratio and [phytate]/ [zinc] ratio in the sample were below the critical levels. The study has shown that matured stems of Opuntia dillenii can contribute greatly towards meeting human nutritional requirement and the high vitamin B 12 content could be of important value in patients with severe sickle cell disease.