Polyvinylidene fluoride (PVDF)-based dielectric energy storage materials have the advantages of environmental friendliness, high power density, high operating voltage, flexibility, and being light weight, and have enormous research value in the energy, aerospace, environmental protection, and medical fields. To investigate the magnetic field and the effect of high-entropy spinel ferrite (Mn0.2Zr0.2Cu0.2Ca0.2Ni0.2)Fe2O4nanofibers (NFs) on the structural, dielectric, and energy storage properties of PVDF-based polymers, (Mn0.2Zr0.2Cu0.2Ca0.2Ni0.2)Fe2O4NFs were prepared via the use of electrostatic spinning methods, and (Mn0.2Zr0.2Cu0.2Ca0.2Ni0.2)Fe2O4/PVDF composite films were prepared via the use of the coating method. The effects of a 0.8 T parallel magnetic field, induced for 3 min, and the content of high-entropy spinel ferrite on the relevant electrical properties of the composite films are discussed. The experimental results show that, structurally, the magnetic field treatment causes the originally agglomerated nanofibers in the PVDF polymer matrix to form a linear fiber chain with different fiber chains parallel to each other along the magnetic field direction. Electrically, the introduction of the magnetic field enhanced the interfacial polarization, and the (Mn0.2Zr0.2Cu0.2Ca0.2Ni0.2)Fe2O4/PVDF composite film with a doping concentration of 10 vol% had a maximum dielectric constant of 13.9, as well as a low energy loss of 0.068. The high-entropy spinel ferrite (Mn0.2Zr0.2Cu0.2Ca0.2Ni0.2)Fe2O4NFs and the magnetic field influenced the phase composition of the PVDF-based polymer. The α-phase and γ-phase of the cohybrid-phase B1 vol% composite films had a maximum discharge energy density of 4.85 J/cm3and a charge/discharge efficiency of 43%.