Abstract The Indian Ocean Dipole (IOD) can influence the El Niño‐Southern Oscillation (ENSO) development 1 year ahead, allowing for prediction of ENSO events up to 14 months in advance. Using observational data sets and numerical experiments, we demonstrate that this IOD‐ENSO connection varies considerably on multidecadal timescales, which are largely controlled by the Atlantic Multidecadal Oscillation (AMO). During the negative AMO phase, sea surface temperature cooling in the tropical Atlantic enhances mean precipitation and convective activity over the tropical western‐central Pacific. This intensifies the Indo‐Pacific Walker circulation and strengthens the IOD‐related surface zonal wind anomalies over the tropical western Pacific. These amplified wind anomalies, in turn, generate larger subsurface ocean temperature anomalies in the region, creating more favorable conditions for the development of ensuing ENSO events. In contrast, these modulations are absent during the positive AMO phase. Our findings enhance the understanding of inter‐basin interactions and are critical for improving ENSO prediction.