Water uptake along the longitudinal direction of wood is notably faster than that along the radial direction. Typically, liquid water absorbed through vessels and/or tracheids travels to the upper sections of wood logs, and the water uptake volume depends on the microstructures of cell types including sapwood, heartwood, latewood, and earlywood. However, wood decay fungi, even in the initial stages of infestation by their existence, can partially alter these microstructures influencing moisture transfer. These structural and biochemical characteristics also impact the hygrothermal analysis of wood structures in the context of building physics. Our study aims to investigate the effects of these wood structure and decay fungi characteristics on moisture transfer and wood decay progress. For this, water uptake tests are conducted along the longitudinal direction of wood samples, and moisture content distributions within the wood samples are estimated through X-ray computed tomography. Several experiments are performed on both sound and inoculated wood samples, and the impact of microstructure and mycelium growth on moisture transfer behavior is discussed based on the experimental findings.