Abstract In this work, an economical, surfactant-free and scalable solution synthesis method at room temperature for self-decorated copper selenide (Cu2-xSe) nanosheets is reported. Structural and morphological characterizations clearly revealed the formation of single cubic phase Cu2-xSe nanosheets in nearly stoichiometric ratio. The tentative mechanism for fabrication of self-decorated Cu2-xSe nanosheets was proposed. Furthermore, nanostructured bulk Cu2-xSe by hot pressing was explored for thermoelectric performance. High electrical conductivity (1.1 × 105 S/m), moderate Seebeck coefficient (87 μV/K) and low thermal conductivity (1.11 W/mK) at 753 K were obtained. The figure of merit (ZT) ~ 0.56 and power factor (PF) ~ 860 μW/mK2 at 753 K showed better performance than some reported Cu2-xSe nanostructured or bulk counterparts under same temperature. Also, theoretically device ZT ~0.16 and efficiency up to 3% could be achieved. The results indicate that this green and novel synthesis process is an alternative to other reported time or energy consuming processes.