In this work, we present a facile and reproducible one-pot approach to synthesize a series of nanosized metal oxides (CdO, PbO, ZnO, SnO and Ga₂O₃) using their corresponding bulk materials as precursors. These nanosized metal oxides were synthesized by heating the mixture of the metal oxide, oleic acid and oleylamine directly, and retained the structure of the corresponding bulk material. For lead oxide, both the original orthorhombic and the tetragonal PbO were successfully synthesized by varying the reaction temperature. The optical properties of nanosized CdO, PbO and ZnO show a significant quantum confinement effect compared with their behavior in the bulk phase. Moreover, we proposed the possible mechanism of the reaction in which the dissolution–recrystallization process provided the dominant contribution.