Offshore wind turbines experience undesirable vibrations under harsh environmental loads, which can cause an increase in the probability of failure and decrease the structural reliability. In addition, there has been a growing interest in highly flexible structural components as the increase of wind turbine capacity, in which large deflection has a significant impact on the structural vibrations. The tuned mass damper (TMD) is one of the most widely utilised vibration attenuation methods in offshore wind turbines due to its easy implementation and cost issues. However, the TMD performance in offshore wind turbine vibration mitigation that considers large structural deflection and geometrical nonlinearity has not been extensively explored yet. The present study has taken large-scale offshore wind turbines as the research object and established a nonlinear dynamic model based on geometrically exact beam theory, in which the key components of offshore wind turbines are all considered and coupled, such as the blade, nacelle, and tower. To mitigate the vibrations, TMD is designed and introduced to the analytical model based on the tower vibration characteristics. The results indicate the effectiveness of employing a nonlinear analytical approach for the design of TMD in vibration mitigation of the offshore wind turbine, which will lay the foundation for nonlinear dynamic analysis techniques on advanced vibration controllers.