The paper reports some experimental data on the effect of halloysite nanotubes (HNTs) content ratio on morphology and thermal properties of poly(3-hydroxybutyrate-Co-3-hydroxyvalerate) (PHBV) bionanocomposites prepared by melt mixing at 2.5, 5 and 10 wt%. The performance of the bionanocomposite samples was evaluated on the basis of neat PHBV. Scanning electron microscopic (SEM) analysis of the fractured surface of the bionanocomposite samples showed the presence of many filler aggregates at 10 wt%. However, a quite homogeneous dispersion of HNTs in PHBV was observed at 2.5 and 5 wt% with the presence of some individual nanotubes. The results indicated also that adding HNTs to PHBV led to an increase in both the crystallization rate and thermal stability of PHBV/HNTs bionanocomposites, being however more pronounced at 5 wt%, which appeared as the optimized filler content ratio.