In this work, the sealing behaviour of bioplastic blends of poly(lactic acid), PLA, and poly(butylene adipate terephthalate), PBAT, at different blow-up ratios (BUR) and blend compositions were studied. Blends samples with 20 and 30 wt.% of PBAT were prepared using film blowing at BUR=1 and 3. Seal strength of film samples was examined using a heating bar sealing machine. The results indicated that the addition of PBAT to PLA increased considerably the sealing window of the blend compare to the neat PLA. However, this effect was much more significant at dispersed phase contents above 20 wt.%. In addition, it was found that increasing the blow-up ratio in samples with 30 wt.% of the dispersed phase increased the sealing temperature window. The surface morphology of these samples was examined using atomic force microscopy and it was found that increasing blow-up ratio changed the morphology of PBAT phase at the surface from a highly elongated fibril-like morphology to disk shape morphology. This increase in the surface area of PBAT phase at the interface is believed to be responsible for the observed wider sealing window of blend sample with higher BUR.