Polymer dielectric possess advantages of mechanical flexibility, low temperature processing, and cost. However, for practical applications dielectric constant of polymers is not high enough. To raise the dielectric constant, polymers are often composited with fillers of various morphologies (one-dimensional, two-dimensional, three-dimensional) and types (inorganic, organic, carbon, conductive, non-conductive). Recently discovered two-dimensional (2D) materials including graphene, transition metal dichalcogenides, MXenes, ferroelectric ceramics, etc. have been discovered. These materials have excellent electrical, mechanical, thermal properties and high specific surface area, which makes these ideal materials to reinforce the properties of polymers, especially dielectric properties. Here, in this review we summarize the latest developments regarding the use of 2D fillers to improve the dielectric properties of polymer composites. We have systematically discussed synthesis of 2D materials, processing of their 2D filler/polymer composites, theoretical background of dielectric properties of these composites, and literature summary of the dielectric properties of polymer composites with various type of 2D fillers.