The effects of compatibilizers and hydrolysis on the mechanical, morphological and rheological properties of polypropylene (PP)/ethylene-propylene-diene monomer rubber (EPDM)/poly(lactic acid) (PLA) blends were studied. The compatibilizers used were polypropylene-g-maleic anhydride (PP-g-MAH) and styrene-ethylene-butylene-styrene-g-maleic anhydride (SEBS-g-MAH) copolymers. Before hydrolysis, mixing the compatibilizers PP-g-MAH (5 phr) and SEBS-g-MAH (5 phr) effectively increased the impact strength of PP/EPDM/PLA (64/16/20) blends without any loss of tensile strength. This result is consistent with the morphological and rheological properties of the PP/EPDM/PLA blends. After hydrolysis, the tensile strength of the PP/EPDM/PLA blends for the PLA-rich compositions decreased sharply until the hydrolysis time was 3 days. This suggests that the mechanical strength of the PLA already lost its mechanical properties, mostly when the hydrolysis time was 3 days under such hydrolysis conditions. The increase in viscosity and decrease in interfacial tension of the compatibilized PP/EPDM/PLA (64/16/20) blends was interpreted with the qualitative picture of the Palierne emulsion model. The interfacial tension calculated from the emulsion model is consistent with the mechanical and morphological properties of the PP/EPDM/PLA (64/16/20) blends.