This research aims at improving barrier properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate), PHBV, by incorporating boron nitride particles (BNPs) via melt compounding. To meet this objective, PHBV nanocomposite samples containing different BNPs were prepared and the effects of BN loading and silane surface modifier on the barrier properties of PHBV nanocomposites were investigated. For all the nanocomposite samples, the permeability is decreased in comparison to the neat PHBV due to both the presence of BN particles and a higher crystallinity. The results demonstrate that barrier properties of the composites were found to increase more for the silanized flake type BN (OSFBN) compared to silanized hexagonal disk type BN (OSBN). The best barrier properties are obtained for the nanocomposite sample containing 2 wt% OSFBN, for which a reduction of oxygen permeability up to 36% was observed in comparison to the neat PHBV. Silane-treated BN nanoparticles yielded nanocomposites characterized by good barrier performance and fine BN dispersion, as shown by SEM investigations. The phenomenological gas permeation models were employed to evaluate the effect of BN particles on oxygen transmission properties. The best approach was found for the relative permeation by using Cussler and Lape models.