Melt blending of poly(butylene succinate) (PBS) with poly(lactic acid) (PLA) to fine tune the mechanical properties of PLA needs to be aware of immiscibility. The present work proposed the random poly(butylene succinate-co-lactic acid) (rPBSL), and for the first time about its multi-functions as compatibilizer, plasticizer, and film clarity enhancer. Based on PLA/PBS (80/20%wt) with rPBSL (3-5 phr), the films obtained show the smooth surface with compatibility and clarity. A significant decrease in T-g (from 52 degrees C to 43 degrees C) and a noteworthy increase in elongation at break (four-fold) confirms the role of plasticizer. A decrease in T-c (from 103 degrees C to 85 degrees C), together with increases in degree of crystallinity and spherulite growth rate with homogeneously dispersed spherulite suggests how the rPBSL effectively induces rapid nucleation. By balancing the crystal and amorphous domains including the initiation of rapid and small spherulites, it is seen that rPBSL performs as a multi-functional additive for PLA/PBS blends. (C) 2016 Elsevier Ltd. All rights reserved.