The carbon nanotube (CNT)/polypropylene(PP) composites have been prepared with the aid of a silane coupling agent (ZFDA, Dow Corning® Z‐6173) and then characterized by electron microscopic, electrical, mechanical, and thermal measurements in order to understand the role of the silane coupling agent in CNT/PP composites. It was experimentally found that the best usage of ZFDA was 20 wt% based on the CNTs. The coupling agent could effectively reduce the percolation threshold to 0.01 wt% from 2.7 wt% for electrical conductivity and at the same time largely improve tensile modulus of CNT/PP composites without sacrificing tensile strength. Being similar to CNTs, the coupling agent‐treated CNTs (named as ZCNTs) could act as a nucleating agent to shift the crystallization temperature of PP to higher temperatures but decrease crystallinity of PP with increasing filler content. The role of the silane coupling agent in these CNT/PP composites has been explored in detail.