The interannual sea level variations in the Northwestern Pacific are significantly tied to the El Niño-Southern Oscillation (ENSO), with opposite responses and asymmetric strength to the south and north of 20°N. Using a 1.5-layer reduced gravity model, we show that the spatial pattern of sea level interannual variations is not sensitive to the existence of the Luzon Strait located at around 20°N, but is dominated by the basin-scale wind stress curl associated with ENSO. Dynamically, sea level variations tied to ENSO are attributed to long baroclinic Rossby wave adjustment driven by wind stress curl in the western/central Pacific, as previous studies have indicated. However, the responses of wind stress curl to ENSO are dynamically different to the south and north of 20°N. In the tropics, the wind stress curl anomaly results from the ENSO event directly, through the Matsuno-Gill response with the transition of zonal wind anomaly at approximately 20°N, while in the subtropics, the wind stress curl anomaly is mainly set up by atmospheric vertical motions through the Hadley Cell. •Inter-annual sea level variations in the Northwestern Pacific are opposite and asymmetric to the south and north of 20°N.•The ENSO-related wind forcing dominates the spatial pattern of regional sea level change.•The tropical response is due to Matsuno-Gill response and the subtropical response is tied to Hadley Cell.