The mechanical properties and morphological changes of poly(lactic acid) (PLA), polycarbonate (PC), and poly(butylene adipate-co-terephthalate) (PBAT) polymer blends were investigated. Several types of blend samples were prepared by reactive processing (RP) with a twin-screw extruder using dicumyl peroxide (DCP) as a radical initiator. Dynamic mechanical analyses (DMA) of binary polymer blends of PC/PBAT indicated that each component was miscible over a wide range of PC/PBAT mixing ratios. DMA of PLA/PBAT/PC ternary blends revealed that PBAT is miscible with PC even in the case of ternary blend system and the miscibility of PLA and PBAT can also be modified through RP. As a result, the tensile strain and impact strength of the ternary blends was increased considerably through RP, especially for PLA/PBAT/PC = 42/18/40 (wt/wt/wt) with DCP (0.3 phr). Scanning electron microscopy (SEM) analysis of the PLA/PBAT/PC blends revealed many small spherical island phases with a domain size of approximately 0.05-1 mu m for RP, whereas it was approximately 10 mu m without RP. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121:2908-2918, 2011