AbstractThis study examines possible links between the western North Pacific summer monsoon (WNPSM) and the North Pacific Gyre Oscillation (NPGO). Our research findings are summarized as follows: (1) In addition to the Central Pacific El Niño, the WNPSM also exerts significant modulation on the NPGO. (2) A time lag is detected in the association between the WNPSM and the NPGO. The WNPSM in JJAS (from June to September) has significant impacts on the NPGO in MAM (from March to May) of the following year. (3) The wave train patterns forced by the WNPSM that are being integrated by the ocean mixed layer may be responsible for the lagged response of the NPGO.