A fluid–structure interaction (FSI) system has been solved using the coupled acoustic structural finite element method (FEM) to simplify the cavitating flow conditions around a hydrofoil. The modes of vibration and the added mass effects have been numerically simulated for various flow conditions including leading edge attached partial cavitation on a two-dimensional NACA0009 hydrofoil. The hydrofoil has been first simulated surrounded by only air and by only water. Then, partial cavities with different lengths have been modeled as pure vapor fluid domains surrounded by the corresponding water and solid domains. The obtained numerical added mass coefficients and mode shapes are in good agreement with the experimental data available for the same conditions. The study confirms that the fluid added mass effect decreases with the cavitation surface ratio (CSR) and with the thickness of the cavitation sheet. Moreover, the simulations also predict slight mode shape variations due to cavitation that have also been detected in the experiments. Finally, the effects of changes in cavity location have been evaluated with the previously validated model.