El Niño-Southern Oscillation (ENSO) is the dominant climate mode of interannual sea surface temperature anomalies (SSTAs) in the tropical Pacific, serving as a pivotal regulator of global climate patterns, with far-reaching socio-economic and environmental impacts. Recent studies highlighted the profound impacts of SST variability in the Northeast Pacific (NEP) on local marine ecosystems and continental climates, garnering considerable attention. Despite being two key drivers of Pacific SST variability, the influence of SSTAs in the NEP (SSTA_NEP) on the development of ENSO remains unclear. This study explores the interdecadal relationship between SSTA_NEP and ENSO from 1961 to 2020 using correlation decomposition and Linear Inverse Modelling, which have been widely applied to capture features of SST variability and predictability. Results indicate that before 1980, SSTA_NEP had a minimal impact on ENSO development. Conversely, from 1981 to 2000, SSTA_NEP variations became more closely linked to ENSO evolution, potentially through the North Pacific Meridional Mode. Nevertheless, since 2001, this connection has weakened, suggesting a complex interplay between SSTA_NEP variability and ENSO. Understanding these changes is important for improving ENSO prediction, which is essential particularly in the context of the ongoing climate change.