Infill walls in reinforced concrete frames are susceptible to failure owing to their brittle nature. Their interaction with boundary columns during earthquakes may also cause shear damage in the columns. It is crucial to employ effective seismic strengthening strategies in order to mitigate the seismic risk induced by the infill walls. In this study, a new strengthening technique, conducted by bonding engineered cementitious composite (ECC) precast panels onto infill walls, was investigated. Three reinforced concrete frames, termed bare frame, infilled frame and strengthened frame, were tested by using the pseudo-dynamic testing method. The test specimens were three-storey, three-bay, half-scaled frames with the central bay having hollow clay brick infill walls. The specimens were subjected to three consecutive ground motions scaled to represent earthquakes with return periods of 144, 475 and 2475 years. The experimental results were compared to observe the influence of the infill walls on the reinforced concrete frames, and to demonstrate the performance of the proposed strengthening technique. It was found that application of ECC panels significantly increased the frame strength and stiffness while allowing the system to have a displacement ductility of about four.