In this work, wood–cement composites (WCC) based on poplar sawdust were developed and fabricated by the extrusion process. The volume fraction of wood particles in the mixes was varied from 23% to 46%. The mechanical properties of these WCC were characterized in compression to determine the maximum compressive strength and the Young’s modulus. In the second part, these Young’s modulus values were estimated in compression using a 3D numerical homogenization which takes into account the variability in wood particle lengths and the random distribution in the mixes. The obtained results show a good agreement between the experimental data and numerical calculations up to a 35% volume fraction. The model’s poor estimation for large volume fractions (over 35%) could be attributed to the experimental sample size, which is not representative for large volume fractions, the percolation of the wood particles into the mixes and the inhibition of the cement setting.