We present a facile one-pot synthesis to prepare ternary Zn xCd1-xSe (x = 0.2, 0.5, 0.8, and 1) nanocrystals (NCs) with high emission quantum yield (QY, 4589%). The effect of Zn content (x) of ZnxCd1-xSe NCs on their physical properties is investigated. The NCs have a particle size of 3.2 nm and face centered cubic structure. However, the actual compositions of the NCs are Zn 0.03Cd0.97Se, Zn0.11Cd0.89Se, and Zn0.38Cd0.62Se when Zn content is 0.2, 0.5, and 0.8, respectively. In terms of the optical properties, the emission wavelength shifts from 512 to 545 nm with increasing Zn content from 0 to 0.8 while the QY changes from 89 to 45, respectively. Partial replacement of Cd by Zn is beneficial to improve the QY of Zn0.2 and Zn0.5 NCs. The optical properties of ternary NCs are affected by compositional effect rather than particle size effect.