The low electrical conductivity and slow rate capability of vanadium oxide limit its utilization in high rate energy storage applications. Many studies are trying to overcome these drawbacks, but it remains a challenge. In this study, we propose a simple strategy to produce conducting polymer-intercalated ammonium vanadate nanofiber composites exhibiting high capacitance and high rate capability. The poly(3,4-ethylene dioxythiophene)-intercalated ammonium vanadate nanofiber composites are produced in a very short time (<4 h) using a sonochemical method. The composite exhibits a high surface area of 85.5 m2 g−1 and excellent electrical conductivity of 4.1 × 10−2 S cm−1. In addition, the lattice distance of the vanadate nanofiber is expanded by insertion of the conducting polymer, which can facilitate transportation of K+ ions into the vanadate nanofibers. These are great benefits for enhancing the specific capacitance and rate capability of the energy storage devices. Therefore, the proposed simple approach can provide a new research direction in the field of high rate energy storage devices.