Preparation of coaxial (core-shell) CdS-ZnS and Cd1-xZnxS-ZnS nanowires has been achieved via a one-step metal-organic chemical vapor deposition (MOCVD) process with co-fed single-source precursors of US and ZnS. Single-source precursors of US and ZnS of sufficient reactivity difference were prepared and paired up to form coaxial nanostructures in a one-step process. The sequential growth of ZnS on US nanowires was also conducted to demonstrate the necessity and advantages of the precursor co-feeding practice for the formation of well-defined coaxial nanostructures. The coaxial nanostructure was characterized and confirmed by high-resolution transmission electron microscopy and corresponding energy dispersive X-ray spectrometry analyses. The photoluminescence efficiencies of the resulting coaxial CdS-ZnS and Cd1-xZnxS-ZnS nanowires were significantly enhanced compared to those of the plain US and plain Cd1-xZnxS nanowires, respectively, owing to the effective passivation of the surface electronic states of the core materials by the ZnS shell.