The existence of a specific intermolecular hydrogen-bonding interaction between poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HH) and (-)-catechin in their blends was demonstrate by Fourier-transform infrared spectroscopy (FT-IR). It was found that the experimentally estimated fraction of hydrogen-bonded carbonyl groups was much lower than the theoretically predicated maximum fraction. Only one glass transition temperature (T g ) occurred in the blends with the compositions detected by differential scanning calorimetry (DSC) being further confirmed by the results of dynamic mechanical thermal analysis (DMTA). The decrease of the melting point (Tm) and the increase of the glass transition temperature of the blends observed by the DSC measurements also suggested the existence of a strong intermolecular interaction, It was interesting to note that as a low-molecular-weight compound, catechin showed a glass transition, which arises from strong self-association. As expected. The crystalline strctune of P(3HB-co-3HH) in the blends showed no change, but the crystallinity of the copolymer component in the blends, calculated by wide-angle X-ray diffraction, decreased with the increase of catechin weight content. Investigated by tensile experiments, the maximum strength and modulus deceased sharply with the increase of catechin content; on the contrary, the elongation changed slowly.