Multifunctional mobile products, such as cellular phones, laptop computers, personal media players, etc., have become smaller and lighter; so the technology of thin-wall injection molding (TWIM) has been highlighted for making lightweight and compact mobile electronic products. Regarding mechanical properties, many portable electronic products should pass the so-called drop test; therefore, the evaluation of the dart (or impact) property of the housing that is made by the TWIM process is crucial for commercializing a product. However, extant research on the effect of injection molding process parameters on the physical properties of TWIM plates is insufficient as yet. Therefore, in this study, the pressure and temperature inside the cavity during the injection molding process are monitored by varying the injection molding process parameters, i.e., the gate size, injection speed, and melt temperature, and the effect of the average flow rate of the molten resin inside the cavity on the dart property of thin-wall injection-molded plates is examined. The dart property of thin-wall injection-molded plates is evaluated by the instrumented dart impact test to differentiate various responses of the load-displacement data during dart tests. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci. 127: 1466-1474, 2013