We report the synergistic and competitive interactions between starch and plasticizers in starch films plasticized by glycerol and xylitol. This resulted into synergistically enhanced and competitively reduced water migration fluxes and effective moisture diffusivities. Low amylose starch was used as sample and the concentration of glycerol and xylitol was varied from 10 to 20 wt% on dry solid basis, either individually, or in (1:1) ratio for making the films. Xylitol showed greater moisture diffusivity, moisture migration fluxes while glycerol showed lower moisture diffusivity and moisture migration fluxes. For low plasticizer concentrations (<15 wt%) the competitive interaction resulted into reduced effective moisture diffusivities and moisture migration fluxes when both plasticizers were present compared to when they were present individually. However, at higher plasticizer concentraions (>15 wt%), glycerol-xylitol plasticized films had greater moisture migration fluxes and effective moisture diffusivities compared to pure ones due to synergistic interaction between starch and plasticizers. Both the moisture migration fluxes and effective moisture diffusivities increased with increase in the plasticizer concentration, however the effective moisture diffusivities showed stronger dependence on moisture concentration rather than the plasticizer concentration. These findings can provide better insights in designing and controlling the vapour barrier properties of starch-based films and packaging.