The two-dimensional germanene material is one of the potential candidates for sensor applications for gases such as VOCs due to its unique structural and electronic properties. The fabrication of these materials is practically not free from defects in the material. Therefore, to better understand the structural and electronic properties of this material when adsorbing VOCs, this study performed DFT calculations of single vacancy-defected monolayer germanene when adsorbing molecules such as acetone, propanol, and toluene. These DFT calculations took into account the intermolecular Van der Waal interactions between germanene and the adsorbed gases. The model of the germanene monolayer is a 4×4 supercell lacking a Ge atom with a distance between the two layers of 30 Å. The results show that the single vacancy-defected monolayer germanene has two stable configurations with a not-toolarge difference in energy. Adsorption of molecules such as acetone, propanol, and toluene onto these monolayers is physisorption (adsorption energies in the range of -0.205 eV to -0.421 eV), however, they also affect the structural and bandgap properties of these monolayers. The bandgap change of the systems in the presence of these adsorptions is not as large (bandgap changes in about 3 meV - 40 meV) as chemical adsorption. Frontier orbitals such as HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) of the VOCs are located quite far from the Dirac points (Fermi level) of the defected germanenes. The negative charge transfer from the defected germanenes to the VOC molecules decreases in the order: Ge31A-Ace > Ge31A-Prol>Ge31B-Ace>Ge31A-Tol>Ge31B-Prol>Ge31B-Tol. The signals of this small change will help in determining the type and concentration of these gases when applying these monolayers as sensors.