In this study, the five-parameter GAB model was adopted to fit adequately for describing experimental sorption isotherm data for pure pullulan, alginate and blend films in the temperature range from 25 to 45 °C. The evaluated M0 of the films ranged from 0.073 to 0.123 with increasing alginate content. The qst of sorption for all samples decreased exponentially with increasing moisture content to 0.1 g/H2O g dry basis, then decreased slowly to near zero at high moisture content, due to a decrease of binding energies between water molecules and sorption sites with increasing moisture content. Pure pullulan films exhibited lowest ∆S values than other samples at high moisture content range (more than 0.17 g/H2O g dry basis), whereas pure alginate films showed the lowest ∆S values with increasing moisture content from 0.05 to 0.17 g/H2O g dry basis. Moreover, ∆Sin values for the tested films decreased to each minimum value (around monolayer moisture content), and then recovered with the rise of moisture content. This could be attributed to the order-disorder extent of the adsorbed water molecules. Furthermore, the enthalpy-entropy compensation suggested that the sorption mechanisms for pure pullulan, alginate and blend films were enthalpy-controlled. The thermodynamic knowledge obtained from this study not only lays a theoretical foundation for designing equipment and standardized drying process for pullulan-sodium alginate based edible films, but also helps to predict their optimum storage conditions.