Different proportions of polyamidoamine (PAMAM) dendrimer were blended with poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) resin in chloroform for film casting. Differential scanning calorimetry and scanning electron microscopy were employed to characterize the PHBV/PAMAM composite films upon stretching and tangential breaking. The results indicated that with the addition of PAMAM dendrimer, the glass transition temperature of the PHBV/PAMAM composite films became more distinct, indicating that the blends had a greater toughness than pure PHBV. The calculated crystallinity values indicated that the crystallinity of the PHBV/PAMAM blends was lower than that of PHBV (0.09-56.18 % vs. 73.18 %, respectively). Moreover, the mechanical performance tests indicated that the addition of PAMAM dendrimer considerably increased the tangential breaking strength of PHBV from 24.08 kN/m to as high as 62.03 kN/m, whereas the tensile strength remained basically unchanged. The optimal toughening effect was observed with a PAMAM dendrimer content of 3.0 phr.