Polyhedral oligomeric silsesquoxane (POSS) cored star-shaped poly(epsilon-caprolactone) (PCL) polymers (POSS-(PCL)(8), SP) were prepared via combination "click" chemistry and ring-opening polymerization (ROP). Then, these star-shaped polymers were melt-blended with commercial linear poly(lactic acid) (PLA) by using laboratory scale twin screw extruder to enhance some of the properties such as toughness of PLA. The thermal, mechanical, and morphological characters of the PLA/SPs were investigated as a function of SP type, i.e. star polymers having different molecular weight with different chain lengths (n = 10, 20, 30, and 50 repeating units) at constant PLA/SP ratio (90/10). The addition of SP enhanced some of the mechanical behavior of PLA. It was established that SP20 (n = 20) is the most appropriate SP-type for improving the mechanical properties of PLA. Also, 1,4-phenylene diisocyanate (PDI) as a compatibilizer was added to blends with constant amount (%1). It observed that PLA/SP blends have maximum effect on toughness of PLA with addition of PDI.