An advanced and inexpensive one-pot method to prepare polystyrene (PS)-barium titanate (BT) films by solution mixing is reported. The process was developed to obtain free-standing films with an increased dielectric constant (epsilon'). Since PS is soluble in apolar solvents, BT nanoparticles (BT-NPs) were surface-modified with palmitic acid (PAc) and embedded within the polymer matrix without affecting homogeneity and smoothness of the composite. The films were prepared by floating method consisting in dropping BT-NPs dispersed in PS/toluene solution on the water surface. After the evaporation of toluene, smooth, free-standing and thermally stable films were obtained with a markedly higher epsilon' compared to the neat PS. PAc modification improved the dispersion of BT-NPs in the apolar phase and prevented their diffusion into the aqueous phase during the toluene evaporation. The proposed film-forming technique makes it possible to modulate the thickness and shape of the films by selecting the quantity and concentration of the organic phase and using various templates, thus opening up a broad range of applications.