In this study, composite systems of multi-walled carbon nanotube (MWNT) and polydimethylsiloxane (PDMS) were prepared by employing acid-treated MWNT (A-MWNT) and amine-terminated PDMS (ATPDMS). A major focus was to investigate the effect of interfacial interactions between acid groups of MWNT and amine groups of PDMS on the rheological properties of the composite systems. It was found that the increase in shear viscosity and dynamic moduli was more pronounced in composite systems containing the pristine MWNT rather than in A-MWNT when the MWNT loading was increased from 0.1 to 0.5 wt.%. However, a synergistic raise of the rheological properties was accomplished by a proper combination of pristine MWNT and A-MWNT at 0.5 wt.% loading. Shear sensitivity of the viscosities was also influenced by the composition of MWNT and the transition from liquid-like to solid-like behavior was discussed in the context of variations occurred in terminal slopes of dynamic moduli of the PDMS/MWNT composite systems.