Abstract: The anomalies of Sea Surface Temperature (SST) over the North Pacific have significant impacts on marine ecosystems and global weather and climate. The North Pacific SST is primarily influenced by ENSO and shows a clear persistence. However, its duration manifests an interdecadal enhancement. Before 2000, the impact of ENSO only lasted until February of the following year; after 2000, however, it could extend until May. Based on reanalysis data, this study explores the characteristics of this interdecadal change and the potential physical mechanisms behind it. The results indicate that the enhanced persistence of ENSO impact on the winter—spring North Pacific SST is mainly controlled by the meridional advection feedback and the sea surface heat flux feedback over the North Pacific. Before 2000, the teleconnection triggered by ENSO had already weakened in spring, leading to high SST due to the heat flux feedback. However, after 2000, the SST anomaly to the west of its normal location during winter allowed equatorial convection to persist near the dateline until the following spring. The persistent convection continuously triggered remote atmospheric teleconnection and resulted in significant cyclonic circulation anomalies over the North Pacific. These anomalous circulations finally led to low SST through meridional advection feedback and heat flux feedback, and thereby enhanced the persistence of the North Pacific SST response to ENSO events.