In this study, a nanocomposite based on a biodegradable polymer poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) reinforced by triethylene glycol mono-n-decyl ether (C10E3) nonionic organoclay (C10E3-Mt) was prepared. The morphology and the thermal and mechanical properties of PHBV/C10E3-Mt were compared with those of PHBV nanocomposites prepared using commercial organically modified montmorillonite Cloisite® 30B (OMt) and raw montmorillonite (Mt). Nanocomposites with 3 wt % nanoparticles were obtained by melt processing. The high level of dispersion with improved interfacial interactions between OMt and polymer led to an increase in the thermal stability and modulus of PHBV. However, this nanocomposite presented a lower strain before fracture, typical of brittle behavior. The transmission electron microscopy (TEM) and wide angle X-ray diffraction (WAXD) results revealed a significant increase in the interlayer spacing of clay for the PHBV/C10E3-Mt nanocomposite, which was favored by the wide expansion of the platelets of the starting nonionic organoclay. This characteristic of C10E3-Mt, together with its hydrophobic behavior, allowed its easy incorporation in the PHBV matrix, thus improving the processing and maintaining a high modulus with increased material toughness.