Abstract A RANS based CFD solver with VOF modeling of free surface is employed to investigate the effects of sloshing and flooding on damage ship hydrodynamics. The numerical study includes three research works, i.e. the simulations of forced roll motion of an intact ship, sloshing of water in tank and forced roll motion of a damage ship. The computed roll moments in the tank and at opening were compared. The coefficient of roll damping was obtained and validated against model test data. The results show that the impact of sloshing on damage ship hydrodynamics is frequency dependent. It becomes significant near natural roll frequency of the tank. The phase differences between hydrodynamic and hydrostatic components are increasing with frequency. The flooding at opening of a damage ship tends to alleviate the sloshing impact.