Observational records reveal that the number of tropical cyclones (TCs) approaching East Asia in July–October is positively correlated with sea surface temperatures (SSTs) in the equatorial and northern off-equatorial central Pacific (CP) oceans, indicating the significant impact of CP El Niño (CP-EN). Through experiments using a Weather Research and Forecast (WRF) model–based regional climate model, this study demonstrates that it is northern off-equatorial CP warming, rather than equatorial CP warming, that effectively induces local anomalous steering flows pertinent to the observed increase in TC activity over East Asia during CP-EN. Sensitivity experiments, in which the prescribed CP-EN-related SST anomaly is confined near the equator, do not capture the observed TC increase over East Asia, whereas those including the off-equatorial region successfully reproduce observed atmospheric and TC variabilities. The off-equatorial CP SST anomaly acts to expand the anomalous cyclonic response in the Philippine Sea farther northward. This produces a tunnel effect in the East China Sea, by which more TCs move to East Asian coastal regions (e.g., east China, Taiwan, Korea, and Japan).