In the present work BaTiO3 nanoparticles (NPs) with different sizes from 150 to 400 nm were prepared by sol–gel hydrothermal method at a temperature lower than 220 °C, and were used as nanofiller for PVDF composites with a loading from 10 to 25 vol%. The morphology of the BT NPs was analyzed by Scanning Electron Microscopy (SEM), and the structural composition was studied by Raman spectroscopy and X-ray diffraction (XRD). The hydrothermal temperature was found to control both the size as well as the phase composition of the BT NPs. The PVDF/BT nanocomposites exhibit enhanced dielectric permittivity and reduced loss tangent, especially with 20 vol% NPs, which contributes to the improvement of the ferroelectric properties. The inclusion of BT in PVDF matrix enhances also the crystallinity of PVDF by acting as a nucleating agent, which further increases the stiffness of the composite. However, at higher volume loading, the reverse tendency was observed with a huge decrease in the PVDF crystallinity at 25 vol%. The simulated PE loop was also investigated for the different loadings mentioned above using an Ising type model based on a 2D lattice and solved by monte-Carlo metropolis method. The results are in good agreement with the experimental results for the polarization hysteresis loops.