Interannual variations associated with El Niño Southern Oscillation (ENSO) in the tropical Pacific are viewed as key drivers of Northeast Pacific marine heatwaves (MHWs), and important sources of their seasonal predictability. However, studies have also shown that Northeast Pacific marine heatwaves are strongly influenced by decadal variability in the tropical and North Pacific, with tropical anomalies contributing to the persistence of these events. In this study, we make use of a Linear Inverse Model (LIM), i.e., an empirical model trained on observations, to examine the relative role of tropical interannual variability and tropical/North Pacific decadal variability in the development of Northeast Pacific MHWs. The dynamical eigenmodes of the LIM operator include both tropical interannual modes, capturing canonical ENSO, and a decadal mode that spans both the North Pacific and the central equatorial Pacific (termed “NP-CP” mode). By selectively “filtering” these modes out of the data, we assess their relative influence on MHW characteristics. Our results indicate that the NP-CP mode was key to the growth of the 2014-16 MHW in the Northeast Pacific, and significantly impacts the intensity of MHWs in this region, while the interannual tropical ENSO modes only influence MHW intensity in the tropical Pacific. These results provide insights on tropical-extratropical interactions at decadal timescales and on the primary sources of Northeast Pacific MHW predictability.