The study focused on the material behavior of two commercial polylactide grades affected by structural changes due to exposure to humid environment. Additionally, the impact of temperature and environment humidity on the moisture uptake and drying process of polymer granulate was examined to evaluate the necessary pre-treatment conditions prior to the polylactide processing. Also some process relevant aspects, such as the impact of polymer pre-drying on its degradation were characterised. In the first part of the experimental work, moisture absorption mechanisms in relation to conditioning parameters were investigated using Karl Fischer titration method. It was shown that the moisture uptake rate correlates with temperature and humidity of the environment. Furthermore, the drying process of polylactide pellets was conducted and analysed by additional melt flow rate measurements to determine the effect of drying conditions on the premature polymer degradation and melt properties. Investigated polymers demonstrated rheological behavior dependent not only on the residual moisture content, but also on drying temperature and time. In the last section of the study flexural and tensile tests were performed in order to determine the influence of moisture uptake on the characteristics of conditioned polylactide. Mechanical strength of polylactide decreased in both, flexural and tensile tests with increasing moisture content in the samples. Moreover, distinctive differences in polylactide mechanical behavior were observed in both tests.