<p>We used the ocean reanalysis dataset SODA2.2.4 to investigate the relationship between the interior branch of subtropical-tropical cells (STCs) in the Pacific Ocean and El Niño-Southern Oscillation (ENSO) over interdecadal timescales between 1930 and 2010, as well as the possible mechanisms involved. Interior transport within the upper pycnocline layers of STCs (InSTC) along 9°S (InSTC9s) shows a significant correlation of −0.54 with ENSO over the study period. However, there is an interdecadal shift in the relationship between InSTC along 9°N (InSTC9n) and ENSO. The correlation coefficient between InSTC9n and ENSO is not statistically significant between 1930 and 1965 (PD1), but is as high as 0.68 (significant at the 95% confidence level) between 1965 and 2010 (PD2). Composite and regression analysis suggests that this shift may be caused by the relationship between InSTC9n and the tropical wind field. During PD1, InSTC9n was driven primarily by the local wind field outside equatorial region, with a relatively weak response to the equatorial wind related to ENSO. In contrast, during PD2, the wind field associated with InSTC9n showed a similar spatial distribution to that of ENSO within the equatorial region, indicating a close relationship between InSTC9n and ENSO. The wind stress curl associated with ENSO drives the anomalous InSTC9n in off-equatorial regions, whose signal can propagate westward in the form of Rossby wave and modulate the thermal structure of the tropical Pacific, favoring the development of ENSO. The possible connection between the Atlantic Multidecadal Oscillation (AMO) and interdecadal changes in the ENSO-InSTC9n relationship was also examined. There is a significant connection between the AMO and the interdecadal change in the relationship between ENSO and InSTC9n; however, the associated mechanism remains to be explored in future studies.</p>