This study was designed for comparative evaluation of phytochemical, proximate, vitamins and mineral nutrient composition of leaf, stem, and root of two medicinal plants- Ipomea involucrata (IP) and Milletia aboensis (MA) - used for the treatment of mental illness in Southern Nigeria. Result of phytochemical screening reveals the presence of alkaloids, saponins, cardiac glycosides, deoxy sugars and resins in all parts of both plants while flavonoids, anthraquinones tannins, terpenes and steroids were unevenly distributed. Organic matter content of all parts of IP and MA fell within a narrow range or 90-99 %. Crude fat was significantly higher (p ˂ 0.05) in both stem and roots than leaves of IP, whereas in MA it was significantly higher (p ˂ 0.05) in leaves than stem and root. Crude protein content of stem and root of IP were similar and about double (and significantly higher (p ˂ 0.05)) than that of the leaves whereas for MA, similar value for leaves was significantly higher than those for stem and root. Vitamins A and E, Fe, Mg, P, Na, K, and Ca, were found in appreciable amounts in all parts of IP and MA. The result of this study has provided both phytochemical and nutritional evidence for the pharmacological roles assigned for the plants and a guide for effective combination of respective plant parts in treatment. It recommends the use of the whole plant of IP for maximum benefit