Although Poly(lactic acid)/polycaprolactone (PLA/PCL) blends have been studied in literature, the deformation mechanism that is related to the toughness increment with respect to pure PLA has not been investigated in detail. The novelty of this work is to understand in depth the correlation between the micromechanical deformation processes occurring in PLA/PCL blends to the macro-mechanical properties, their morphology and their fracture mechanism.