Abstract: According to the signal separation and reconstruction of the Multi Taper Method-Singular Value Decomposition (MTM-SVD) method, this study investigates the impact of interannual SST forcing associated with the El Niño-Southern Oscillation (ENSO) on precipitation over the middle and lower reaches of the Yangtze River Basin (MLYR), along with the possible underlying mechanisms. The results show that the MLYR precipitation is associated with the tropical Pacific SST at two distinct periods, i.e., the quasibiennial (2.4-year) and quasiquadrennial (3.7-year) periods, which is related to the CP-type and EP-type El Niño, respectively. These two types of El Niño trigger different atmospheric circulation responses in East Asia, and both have a positive impact on the interannual variability in the precipitation over the MLYR. During the quasibiennial period, the mature phase of CP-type El Niño leads to an East Asian–Pacific atmospheric teleconnection. During the quasiquadrennial period, the mature phase of EP-type El Niño results in a meridional dipole-like distribution of atmospheric activity centers over East Asia. Additionally, both types of El Niño events trigger the western North Pacific anomalous anticyclone (WNPAC) during their mature phases. These atmospheric circulation systems enhance the moisture transport from the South China Sea to the MLYR, which subsequently increases local precipitation. Furthermore, our case analyses show that there is a difference in the relative contribution of the quasibiennial and quasiquadrennial periods to the MLYR precipitation variations in 2002. In the spring of 2002, the quasiquadrennial period contributed to an increase in precipitation over the MLYR, while the quasibiennial period weakened it. A contrasting situation was seen in the autumn of 2002. This study refines our understanding of how the multi-timescale forcing of the tropical Pacific SST affects the interannual variability of MLYR precipitation. The outcomes and conclusions of the study help improve the accuracy of local precipitation forecasts in the MLYR.