Aim: To investigate the proximate composition and phytochemical constituents of matured Carica papaya seed. Study Design: Proximate composition was determined on Carica papaya seed powder while extracts for phytochemical analysis were obtained, in turn using five different solvents of varying polarity, namely n-hexane, chloroform, ethyl acetate, methanol and water. Place and Duration of Study: Department of Biochemistry, Faculty of Basic Medical sciences, Bayero University Kano, Nigeria. The study was carried out between March- April, 2019. Results: The proximate composition of matured Carica papaya seed showed it contained crude fat (27.72%), carbohydrate (23.34%), crude fibre (21.25%), ash (10.25%), crude protein (9.65%) and moisture (7.34%). Qualitative phytochemical screening of Carica papaya seed extracts detected major phytochemicals except anthraquinones and quantitative analyses of these phytochemicals in all the five extracts showed that flavonoids was the most abundant phytochemical with 38.68%, 35.85%, 36.76%, 34.04% and 23.50% for methanol, aqueous, chloroform, n-hexane and ethyl acetate fractions respectively while tannins was the least abundant phytochemical with 0.03% for methanol extract, 0.04% for n-hexane extract, 0.09% for aqueous and ethyl acetate extracts, and 0.14% for the chloroform extract. Conclusion: Seeds of matured Carica papaya contain major nutrients that may be useful in nutrition. The presence of phytochemicals such as flavonoids, alkaloids and saponins in considerable quantities explained the medicinal activity of the plant material as encountered in its therapeutic uses.