A novel one-step soft solution-processing route called the solvothermal-copolymerization technique was successfully developed for in situ fabrication of polystyrene (PS)/CdS nanocomposites embedded with CdS nanowires in ethylenediamine media at lower temperatures (80-140 degreesC). In this route, the polymerization of the monomers and the formation of the CdS nanocrystallites occur simultaneously in a certain temperature range. The results of X-ray powder diffraction, transmission electron microscopy, and high-resolution transmission electron microscopy confirmed that the embedded CdS nanowires, with diameters of 4-15 nm and lengths up to several micrometers, have [001] preferential orientation. Both temperature and solvent were found to play a key role in the synthesis of the nanocomposites. The produced novel hybrid nanocomposites display obvious quantum size effects and interesting fluorescence features. The spectroscopic properties of the PS/CdS nanowire nanocomposites were found to be sensitive to synthetic conditions, including the concentrations of Cd2+ or the monomer, temperature, and reaction time.