Fully bio-based polyamide 11 (PA11) were successfully melt-blended with poly (vinyl alcohol) (PVA03, PVA05, PVA08 and PVA14) having varying degrees of polymerization (Dp) to prepare PA11xPVAzy blend. The PA11xPVA03y, PA11xPVA05y, PA11xPVA08y and PA11xPVA14y films demonstrated the lowest oxygen transmission rates (OTR), fractional free volume (Fv) and mean volume of the free volume holes (Vf) values, when the PVA content of each PA11xPVAzy series reached a corresponding critical concentration of 27.5, 22.5, 17.5 and 12.5wt%, respectively. It is worth noting that lowest OTR, Fv and Vf values obtained for optimal PA11xPVAzy films reduced significantly, as DPs of PVA decreased from 1400 to 800, 500 and 300. In fact, a 1.07 cm3/m2.day.atm OTR was obtained for the optimal PA1172.5PVA0327.5 film, this OTR is near that of the most often used high barrier polymer (i.e. ethylene-vinyl alcohol copolymer). As evidenced by dynamic mechanical analysis and other experimental characterizations of the PA11xPVAzy blends, PA11 and PVA are compatible to some extent, when their PVA are ≤ the corresponding critical concentration. Presumably, the significantly improved OTR for PA11xPVAzy blend films with optimized compositions are ascribed to the considerably reduced local free-volume characteristics.