The effect of processing conditions on fiber length degradation was investigated in order to produce higher performance composites. For this aim. Nylon-6 was compounded with glass fibers in a twin screw extruder for various combinations of screw speed and feed rate. Collected samples were injection molded and izod impact and tensile strength tests were performed in order to observe the effects of fiber length on mechanical properties. Also, by using the extruded and injection molded samples. fiber length distribution curves for all experimental runs were obtained. Results show that when the shear rate is increased through the alteration of screw speed and feed rate the average fiber length decreases.