In this paper, a new retrofit method, which is called “Hybrid Wall Technique”, is proposed for retrofitting soft-story RC frames. In the proposed technique, steel plates encase the boundary RC columns, and connect to additional steel plates at the bay of the frame with the help of high-strength bolts. After installation of steel plates and high-strength bolts, which are also used as formworks, the additional concrete is cast. Structural performance of the proposed method is verified by experimental investigations conducted on one-bay one-story RC frames. One non-retrofitted frame and three frames retrofitted by thick or thin hybrid walls were evaluated experimentally.