The pursuit of flexible dielectrics with high permittivity and low loss is favored by next-generation charge storage devices. Based on the micro-capacitor model, polymer/conductive filler dielectric (PCD) composites show the most potential in achieving high permittivity. However, a remarkable increase in dielectric loss generally limits their practical applications, due to inevitable contact between neighboring conductive particles. In this work, the carbon nanotubes (CNTs) were coated by polydopamine (PDA) through the self-polymerization of dopamine hydrochloride (DAH) monomer and the coating thickness could be controlled by changing the DAH/CNT ratios. When the coated CNTs were incorporated into the PVDF matrix, the electrical conductivity tended to be reduced with the thickening of PDA coatings, implying that undesired current leakage could be effectively suppressed. In addition, the effects of the coating thickness, loading contents and dispersion status of as-treated CNTs on dielectric properties of the composites were investigated. Results demonstrated that the composite filled with 0.2wt% coated CNTs (DAH/CNT weight ratio: 0.2) could obtain a high permittivity of 315 and a low loss factor of 0.35. Accordingly, it can be regarded as one of strategies to make the PCD composites achieve balanced dielectric behaviors.