Nano-SiO2 was introduced into in-situ composites of polycarbonate (PC) and a thermotropic liquid crystalline polymer (TLCP) using a twin-screw extruder. The rheology of these composites was characterized with capillary rheometry, and the morphology of the dispersed TLCP observed with scanning electron microscopy. The rheological data revealed that the viscosity decrease of PC melts by only the addition up to 20 wt% TLCP remained smaller than 30%, while it became similar to 48% upon further addition of only about 1 wt% nano-SiO2 and larger than 60% upon similar to 9 wt% nano-SiO2 filling, in contrast to a 50% viscosity increase of PC melts with increase in nanosilica loading up to similar to 9 wt%. These silica-filled composites exhibited markedly low viscosity, especially at relatively high shear rates. The morphology of TLCP extracted from unfilled and silica-filled composites indicated that the largest viscosity reduction was correlated well with the fibrillation of TLCP droplets enhanced by nano-SiO2. The TLCP/SiO2/PC composites exhibited rheological hybrid effect with fillers at nanometer scale.