The CuSe and Cu_(2-x)Se crystallites were successfully synthesized by triethylene glycol (TEG) solution thermal decomposition using triethylenetetramine (TETA) as the reducing agent and polyvinylpyrrolidone (PVP) as the capping agent at 230℃ for 40 minutes. The crystalline structure, microstructure, and chemical composition were investigated using X-ray diffractometer (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). We investigated the effects of TETA additive on crystal phase and morphology. When the TETA additive was 0.4 vol% or 1.2 vol%, the copper selenides are pure CuSe and Cu_(2-x)Se single phase.