Enhancement of the energy harvesting performance and dielectric constants of PVDF-based capacitors was realized by incorporating 16 wt% of surface-treated BaTiO₃ hollow nanospheres (HNSs) in comparison with the pristine PVDF. The fabricated BaTiO₃ HNSs with particle sizes of ca. 20 nm and BET surface area of 297 ㎡ g^-1 were treated by three different surface-modifiers. The changes in crystallinity of the PVDF containing the surface-treated BaTiO₃ HNSs were induced by both enlarged surface areas and increased surface functionality of the HNSs. Effects of such surface functionalities on the crystalline, dielectric, and energy harvesting performances of the nanocomposites were systematically investigated to identify the optimal surface modifier to enhance the energy density of the nanocomposites. Consequently, these changes in crystallinity led to higher dielectric constants (ε´≈109.6) and energy density (U_e≈21.7 J cm^-3) with highly retained breakdown strength (E=3.81×10³ kV cm^-1) compared to pristine PVDF (ε´≈11.6 and U_e ≈2.16 J cm^-3 at 3.98×10³ kV cm^-1), indicating their potential as high energy density capacitors.