High-dielectric-constant (high-epsilon) ceramic/polymer composites are an important class of advanced functional materials due to their applications in energy storage fields, such as embedded capacitors. Here, we synthesized novel polymer-derived silicon carbonitride (SiCN)-filled polyvinylidene fluoride (PVDF) composites by the tape-casting method. For comparison, commercial BaTiO3-filled PVDF composites were synthesized following the same process. The SiCN/PVDF composites showed much higher epsilon than the BaTiO3/PVDF composites over a broad frequency range (10(-1)-10(6) Hz). Furthermore, the SiCN/PVDF composites showed ultrahigh epsilon at low frequencies. The epsilon of the 40 vol% SiCN/PVDF composite was as high as 2600 at 10(-1) Hz. Although the dielectric breakdown strengths of the SiCN/PVDF composites were slightly lower than those of the BT/PVDF composites, the calculated maximum energy storage density of the 40 vol% SiCN/PVDF composites (17.5 J cm(-3)) was much higher than that of 40 vol% BT/PVDF (0.773 J cm(-3)) at 10(-1) Hz. This is the first report on the use of polymer-derived ceramics as a component of ceramic/polymer composites. The results indicate that the polymer-derived SiCN ceramics can serve as promising ceramic fillers for high-epsilon composites and that the obtained SiCN-filled composites have promising applications in energy storage fields.