In this work, the crystal structure, thermal conductivity, as well as dielectric and electrical properties of poly(vinylidene fluoride-co-chlorotrifluoroethylene) [P(VDF-CTFE)] filled with two different carbon nanofillers including exfoliated graphite nanoplates (xGNPs) and multi-walled carbon nanotubes (MWCNTs) have been compared. The xGNPs and the MWCNTs were well dispersed in the P(VDF-CTFE) matrix using a simple solution-blending process. The xGNPs have the ability to induce the large amount of useful polar and crystal phases for P(VDF-CTFE) via the relatively strong interfacial interaction between their functional groups and the dipoles of P(VDF-CTFE), while the MWCNTs only produce the relatively low amount of crystal phases for P(VDF-CTFE) due to their weak -dipole interactions with P(VDF-CTFE). It was found that both the electrical conductivity and dielectric properties of xGNPs/P(VDF-CTFE) composite were better than those of MWCNTs/P(VDF-CTFE) composite. The thermal conductivities of xGNPs/P(VDF-CTFE) composites were much higher when compared with those of MWCNTs/P(VDF-CTFE) composites at the same filler content, which is probably owing to the better compatibility between xGNPs and P(VDF-CTFE). For example, the thermal conductivities of xGNPs (5wt%)/P(VDF-CTFE) composite and MWCNTs (5wt%)/P(VDF-CTFE) composite were 0.83W/mK and 0.43W/mK, respectively.