Polymer composites reinforced with wood cellulose fibres have been studied for several decades, mainly motivated by the low cost, renewability and abundant availability of the fibres. Other well-known advantages with cellulose fibres are the interesting mechanical properties and the low abrasive nature. A major disadvantage with making use of cellulose fibres in polymer composites is the difficulty with mixing and processing of such composites. While melt processing of cellulose fibre composites may cause significant shortening of the fibre length, it has also been seen that better fibre dispersion improved the mechanical properties of the composite. A previous study indicated improved fibre dispersion when using a barrier screw for extrusion mixing of a highly beaten cellulose pulp in wet state with an ethylene acrylic acid copolymer (EAA). Here, the low melting point of EAA (80-110°C) and the improved hydrophilicity (compared to many polyolephins) make this polymer interesting as a matrix for cellulose fibre composite. In this study, we further investigate the influence of the water content when extrusion mixing wood cellulose fibres with EAA, as seen on the mechanical properties of the final composite. Composites consisting of 20 to 70 vol% dry content of highly beaten spruce cellulose fibres were blended with an EAA in a mixing chamber. During mixing, the water content was varied between 20 to 50%. The mixed compounds were then dried, followed by compression moulding into thin samples. Tensile measurements on compression moulded samples showed that the tensile modulus increased significantly with increasing fibre content, also that the modulus was improved with increasing water content at mixing.