Poly(lactic acid) (PLA), a bio-based aliphatic polyester, has been of interest for biodegradable packaging applications in recent years. However, due to its relatively high Tg and rigid structure, PLA can not satisfy the desired flexibility to use in flexible-packaging applications. Therefore, it needs to be plasticized. In this study, the efficiency of four different types of citrate ester based plasticisers, i.e. tributyl citrate (TBC), acetyl tributyl citrate (ATBC), tri-2-ethylhexyl citrate (TEHC), triisodecyl citrate (TIDC), were examined. As the control, poly(ethylene glycol) (PEG MW: 8000 g/moles), a highly recommended plasticizer for PLA, were utilized. Melt mixing method was used as the processing method. The plasticizer ratio was kept at 10 wt%. Pre-dried PLA and the plasticizers were compounded for 3 minutes at 180°C by using a laboratory twin-screw compounder (DSM Xplore 15 cc Micro-compounder). At the end of mixing time, blend was subsequently injection molded with DSM Xplore 12 cc Injection Molder. Differential scanning calorimetry (DSC), tensile testing and dynamic mechanical analysis (DMA) were used to investigate the thermal, mechanical and viscoelastic properties of the neat and plasticized PLA compounds. DSC results showed that the plasticizers decreased the Tg of PLA with respect to their molecular structures. The reduction in Tg was the highest in PLA/TBC system, whereas it was the lowest for the PLA/TIDC, with respect to the molecular weight of the plasticizers. Mechanical tests showed that the elongation at break values for the plasticized PLA was in the order of TBC = ATBC > TEHC > TIDC. In addition, a reverse order was obtained for the yield strength values. The moduli obtained from DMA supported these findings. It can be concluded that the molecular weight and chemical architecture of the citrate ester based plasticizers play a crucial role on the miscibility of the plasticizer that in the end affects the performance of plasticized PLA.