The influence of humidity on the density, shear elastic module, viscosity, and thickness of the mushroom Pleurotus eryngii and Ganoderma lucidum mycelium films was studied. These data were obtained by comparing the theoretical and experimental frequency dependencies of the complex electrical impedance of bulk acoustic wave (BAW) resonator loaded by mycelium film using the least-squares method. This procedure was performed for the BAW resonator with pointed films for the relative humidity range of 17%–56% at the room temperature. As a result, the changes of the density, shear elastic module, viscosity, and thickness of the films under study, due to the water vapor adsorption, were determined. It has been established that the properties of mycelium films are restored after removing from the water vapor. So, these results show the possibility of using investigated mycelium films as sensitive layers for acoustic humidity sensors.