Rod-shaped ZnO crystals were synthesized by chemical precipitation method from aqueous solution. Carboxymethyl inulin (CMI) was used as an additive in ZnO synthesis reaction, and particles with differing sizes and structures were obtained. CMI hindered crystal growth in the length axis of the rods, while growth on the lateral axis was not suppressed. ZnO crystals synthesized with varying CMI concentrations were incorporated into PHBV (3-polyhydroxybutyrate-co-3-hydroxyvalerate) matrix and the effect of the particles on thermal and mechanical properties of the polymer were investigated. Considerably good particle dispersion was obtained in the polymer matrix by melt-extrusion method. ZnO particles did not seem to affect main crystal structure, melting temperature and crystallization temperature of PHBV, whereas they had a retarding effect on crystallization. The addition of ZnO particles into PHBV increased elongation at break and toughness values, along with the decrease in the degree of crystallinity. Tensile strength was also increased without a significant change on the stiffness. Thermal degradation temperatures were observed to slightly decrease with ZnO addition compared to neat PHB; however, degradation peak temperature was still considerably above the melting temperature of the polymer.