Polypropylene/poly(3-hydroxybutyrate-co-hydroxyvalerate) blend (PHBV) and polyethylene/PHBV blend were prepared by twin screw extruder using preformed copolymer (EVOH-g-PHBV) as compatibilizer or with functional polyolefins that can react in situ with the PHBV phase to form POs-g-PHBV. Scanning electron microscopy shows that by using either EVOH-g-PHBV preformed copolymer or formed copolymers in situ both emulsify the phase interface and reduce the interfacial tension, which result in an enhancement on the mechanical properties of compatibilized blends. Enhancement is more or less pronounced depending on the used PO matrix. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013