Poly(L-lactide)/ethylene-co-vinyl acetate (PLLA/EVA) blends with different contents of Vinyl Acetate (VA) in EVA phase were prepared through melt blending process. Although the composition of the blends was invariant (70/30), different phase morphologies were observed, namely, sea-island morphologies for the blends with VA contents of 7.5, 18, and 28 wt %, whereas approximate co-continuous morphology for the blend with VA content of 40 wt % was observed. The interfacial interaction between PLLA and EVA was visualized by Fourier transform infrared and rheological measurements. The nonisothermal and isothermal crystallization behaviors of the blends were investigated by wide angle X-ray diffraction, Differential scanning calorimetry, and polarization optical microscope. Post-thermal treatment was applied to improve the crystalline structure of PLLA. The results show that all the samples are mainly in amorphous state during the injection molding process. However, annealing promotes the second crystallization of PLLA matrix, leading to the improvement of the crystalline structure. Especially, the effect of annealing on crystalline structure of PLLA matrix is greatly dependent on the VA content of EVA. As expected, addition of EVA results in the improvement of the ductility and fracture toughness of the blends. The decreased tensile modulus and tensile strength can be enhanced through annealing process. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 2688-2698, 2011