A series of poly(ethylene-co-vinylalcohol)(PE-VOL)/poly(D,L-lactic-co-glycolic acid (PD,L-LGA) blends with different compositions was prepared by solution casting, and its miscibility was proved through viscosimetry and differential scanning calorimetry (DSC) methods through a positive value of α (San et al. Eq.) and negative value of χ1,2 (Nishi-Wang Equation). XRD analysis of the PE-VOL/PD,L-LGA system revealed a homogeneous distribution of PE-VOL molecules aggregated in the PD,L-LGA matrix and the crystalline structure of the semi crystalline copolymer was conserved in the blend in aggregated form. It also revealed that the amorphous copolymer dispersed in the blend acted as a weak nucleating agent. The non-isothermal crystallization kinetics of neat semi-crystalline copolymer and the blend was used to describe the crystallization process using the Ozawa approach. The thermal stability of these materials was investigated by the thermal gravimetry analysis. The isothermal decomposition of copolymers and their blend were carried out by high resolution mass spectrometry using direct-analysis-in-real-time method. Relevant results that could highlight the miscible character of this blend are revealed through comparison of the different fragments resulting from the decomposition of the blend with those of the pure components.