In this work, graphene nanoplatelets (GNPs) with spindle-like CaCO3 (CGNP) deposited on their surface were used as fillers to produce CGNPs/polytetrafluoroethylene nanocomposites. The CGNPs and their nanocomposites were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and differential scanning calorimetry. The effect of the CGNPs on the mechanical, electrical, and frictional properties of the nanocomposites was also investigated and discussed. It is found that the tensile strength and elongation at break of the nanocomposites are improved by 44 and 26%, respectively, at a percolation threshold of 1 wt% due to the heterogeneous nucleation of CGNPs. The electrical conductivities of the nanocomposites increase with increasing the loading of CGNPs, and the conductive network of the nanocomposites starts to form when the filler loading up to 10 wt%, which is revealed by Raman mapping. The frictional properties of the nanocomposites also increase with increasing CGNP loading due to the well distribution and interfacial interaction between CGNPs and PTFE matrix.