In this paper, the seismic behaviors of assembled monolithic engineered cementitious composite (ECC)/steel reinforced concrete (RC) composite frame and RC frame were investigated based on both experimental and simulational methods. During the horizontal cyclic loading test, it was found that the ECC/RC composite frame generally kept its integrity while concrete spalling and crushing were observed for RC frame. The energy-dissipating capacity, ductility as well as stiffness for ECC/RC composite frame are higher than those for RC frame. A new finite element (FE) model was also proposed and the accuracy was verified with the experimental results. Based on the proposed FE model, the failure processes of both ECC/RC composite frame and RC frame were analyzed and compared. It was found that the maximum plastic ratio of steel reinforcements for ECC/RC frame is 2.3 times higher than that for RC frame, indicating ECC/RC composite frame has better deformation compatibility between different components. The influences of different parameters on the cyclic behaviors of ECC/RC composite frame, i.e., ECC compressive strength, ECC tensile strain, axial load ratio, and ECC width ratio were also discussed in this paper.