This study investigates the seismic mitigation performance of improved rotational two-level friction damper (IRTFD) for reinforced concrete (RC) frame structures. A numerical material model “IRTFD material” was developed in OpenSEES to simulate its multi-level hysteretic behavior and the mechanical expression of “IRTFD material” was proposed. Besides, the details of the prototype structure and the modeling strategy have been introduced. A total of three structures, including a bare frame, a frame with traditional friction dampers (TFDs), and a frame with IRTFDs were analyzed through nonlinear time history analysis under seven ground motions spanning multiple seismic intensities. The numerical results demonstrate that the IRTFDs outperform TFDs in mitigating peak inter-story displacement and residual inter-story drift. Due to the additional stiffness and additional energy dissipation of IRTFD at the second-level working stage, the seismic mitigation effect of IRTFD on the structure is more significant under moderate and strong seismic conditions. Nevertheless, the inherent higher stiffness of IRTFDs inadvertently amplifies peak floor acceleration in the frame with IRTFD.