Reinforced concrete frame (RC) structures with soft first storeys are one of the most common structural systems in the world. However, when these buildings are subjected to strong earthquakes, the seismic forces concentrate in the first storey, resulting in large inter-storey drifts. This can lead to significant damage or even collapse. In this paper, the seismic performance of a four-, five-, and six-storey RC frame building in New Tiba City is analysed for three different cases: a bare frame, a soft first storey, and a fully infilled frame. Pushover analysis is used to compare the capacity curves of the considered cases. The results show that the soft first storey cases have significantly lower seismic performance than the fully infilled frame case. To improve the seismic performance of the soft first storey cases, reinforced concrete jacketing is conducted. The results show that jacketing can significantly improve the seismic performance of RC frame buildings with soft first storeys.