The wood of dead trees is an essential element of the forest ecosystem, as it affects the characteristics of forest soil properties. The present study aimed to determine the influence of dead alder and aspen wood in various stages of decomposition on the physical properties of forest soil. The study was carried out in the area of the Czarna Rózga reserve in central Poland. Alder and aspen logs in third, fourth, and fifth decay classes were selected for the study. Wood and soil samples under the direct influence of wood and soil samples without the influence of deadwood were collected for laboratory analyses. Physical properties of the soil samples, such as bulk density, moisture, porosity, field capacity, and air capacity were analyzed. Water repellency (WR) was also determined. Our study confirmed that decomposing wood influenced the physical properties of forest soil. Organic matter released from decomposing wood penetrates the soil and alters its physical properties. By releasing organic matter from deadwood, it is possible to stimulate the formation of soil aggregates, improve soil porosity, and significantly increase the number of micropores, which results in the retention of more water in the soil.