Global warming is one of the issues in the world, which is mainly due to the burning of fossil fuels. Thus, alternative energy is now paramount in the 21st century. In Korea, the tidal currents in the southwestern sea have a wide range of currents that are available for tidal current power generation. Single rotor turbines can obtain a theoretical maximum power coefficient of 59.3%, whereas dual rotor turbines can attain a maximum of 64%. In this study, the performance and efficiency of a counter-rotating tidal current turbine is investigated when changing the front and rear blade angles at different water velocities. The investigation was conducted by using Computational fluid dynamics (CFD) and experimental methods highlighted in this study. When varying these parameters, changes in the streamlines were observed in the CFD results. The changes in flow stability over the blade surfaces observed in the numerical results were reflected in the power and power coefficient graphs presented in this study. The results obtained by the experiments were also shown to be in good agreement with the CFD results.