Rheological behaviors of hybrid composite systems consisting of liquid crystalline polymer (LCP), short glass fibers and toughenednylon 66 were characterized with capillary rheometry. The results were compared with the rheological behavior of untoughened nylon/glass fiber/LCP hybrid composites to establish the role of elastomers and glass fibers on LCP fibrillation. Results showed that, compat-ibilization of nylon and LCP in the presence of MA-grafted elastomer and glass fibers is the primary factor promoting LCP fibrillation intoughened glass fiber filled hybrid composites. Glass fibers serve as inert fillers modifying the interfacial interaction between the tough-ened nylon 66 and LCP phases. Morphology of the rheometer extrudates observed with scanning electron microscopy was consistentwith the predictions from rheological results. The influence of rheology and morphology on the mechanical properties was also exam-ined. It was found that tensile strength of toughened hybrid composites improved with the addition of glass fibers and on the other handthe strength of untoughened hybrid composites deteriorated with the glass fiber addition.