In this study, the effects of filler geometry on the electrical conductivity and electromagnetic interference (EMI) shielding properties of poly(trimethylene terephthalate) (PTT) composites filled with graphene nanosheets (GNSs), carbon nanotubes (CNTs), and GNS-CNT hybrid nanofillers have been investigated. The GNSs, CNTs, and hybrid GNS-CNT were well dispersed in the PTT matrix using a simple coagulation process. GNSs were prepared from graphene oxide (GO) through hydrazine reduction, and thermal reduction of GO at two different temperatures of 1050 and 1500 A degrees C. PTT filled with different aspect ratios and oxygen functional groups of GNS were also prepared in order to compare the electrical conductivity and EMI shielding properties. The aspect ratios of GNSs and CNTs were estimated by using an ellipsoid model. Percolation scaling laws were applied to the magnitudes of conductivity to reveal the percolation network and filler dispersion. The percolation exponent of the PTT/GNS composites was larger than that of the PTT/CNT composites. The percolated filler-filler network at which the percolation exponent changed was correlated with the filler geometric structure. GNS-CNT hybrid nanofillers formed a complex double brush structure in the PTT/GNS-CNT composites. The geometric structure, aspect ratio, and intrinsic conductivity of carbon nanofillers affected the electrical percolation threshold and EMI shielding efficiency of the composites.