The subtropical northeastern Pacific (SNEP) acts as a bridge conveying information between the North and tropical Pacific. While most studies have investigated the SNEP sea surface temperature (SST) interannual variability, less attention has been paid to the pronounced decadal variability in this region. Here, by analyzing observational data and an ensemble pacemaker simulation, we investigate SNEP SST decadal variability in terms of atmospheric forcing processes. We find that both tropical Pacific-forced and internal (independent of tropical Pacific forcing) atmospheric variability play important forcing roles. In particular, tropical Pacific-excited Aleutian low variability, whose center of action shifts southeastward compared to the climatology, contributes to forcing SNEP SST decadal variability. This contribtution could offer an important source for the predictability of SNEP SST decadal variability.