The orientation structures of both carbon nanotubes (CNTs) and polymer molecular chains in the skin core structure of polystyrene/multiwalled carbon nanotube (PS/MWCNT) nanocomposite melt-injection-molded pellets were examined. Scanning electron microscopic (SEM) and transmission electron microscopic (TEM) images clearly show the MWCNT preferred orientation along the melt shearing direction, while polarized Raman spectroscopy results consolidate the MWCNT preferred orientation in each of the skin, medium, and core layers of the injection-molded pellets. By infrared dichroism measurements, a preferred orientation of the PS side groups (phenyl rings) perpendicular to the melt shearing direction was deduced at all depths of the present injection-molded nanocomposite pellet. Meanwhile, the MWCNTs have little effect on the random orientation of the PS main chain (-CH2- groups) with a dichroic ratio near unity.