Injection molding of reinforced thermoplastic materials is increasingly used in order to obtain high specific mechanical properties and good surface finishing. In this work a rapid heat cycle molding (RHCM) technology was employed to study the influence of injection molding parameters on fibers orientation and mechanical properties of thermoplastic fiber reinforced injection molded parts. X-ray computed tomography (CT) was employed to allow a direct observation of the fibers orientation. The injection molding parameters investigated were mold temperature, injection speed and part thickness. The experiments show that the mechanical properties are maximized by high part thickness, low mold temperature and injection velocity. However, the variation of the investigated injection molding conditions had a negligible effect of fibers orientation.