Flexible polymer composites with high dielectric constant are highly desirable for electrical and electronic applications. This work demonstrated the preparation of high-dielectric-constant (high-k) and low-dielectric-loss flexible composites by incorporating reduced graphene oxide (rGO) and the colossal-dielectric-constant CaCu3Ti4O12 (CCTO) particles in poly(vinylidene fluoride) matrix via solution processing. The three-phase composites combine the merits of each two-phase composite while avoiding the demerits of the two-phase composites. A high dielectric constant (similar to 40.4) and relatively low dielectric loss tangent (similar to 0.08) at 1 kHz were achieved when rGO and functionalized CCTO were 0.61 vol% of 12.5 vol%, respectively. The enhanced dielectric properties of the composites may originate from both induced polarization effect and intrinsic high dielectric constant of rGO, and the tunneling effect between rGO sheets play an important role in electrical conductivity and dielectric loss of the composites. It is believed that the ceramic/rGO/polymer three-phase hybrid strategy can be used to design and fabricate high-k composites with desirable flexibility and dielectric applications.