The project aims to develop a methodology to study the variation in properties of wood polymer composites (WPC’s) with/without surface treatment at different humidity conditions. The project aims to investigate the behavior of biocomposites at 50%, 80%and 100% relative humidity (RH). Also to clarify if the hydrophilization effect helps to preserve the structural integrity of the materials for longer periods at these conditions. The comparison between biocomposites comprising polypropylene (PP) with both untreated wood fibers (WF) or FibraQ (hydrophobic surface-treated wood fibers from Biofiber Tech) was made. The focus was on the mechanical properties, water absorption, macro- and microstructures. The results show that PP comprising FibraQ exhibits lower moisture uptake than the PP comprising untreated WF at high relative humidity conditions. The mechanical properties did not seem significantly affected by the surface treatment at high relative humidity conditions. It is also concluded that since the study only ran for four weeks, there was not enough time to fully understand the influence of moisture uptake over the materials’ properties.