Abstract The mid‐tropospheric winter North Pacific storm track (NPST) underwent an interdecadal transition from weak to strong in the mid‐1980s and exhibited a significant intensification trend. Using climate model outputs, this study investigates the contributions of external forcing and internal variability to the NPST intensification. The result indicates that externally forced NPST trends in historical simulations are not significant. Thus, the dominant cause of the NPST intensification trend is internal variability rather than external forcing. Large‐ensemble simulations reveal that negative‐phase western Pacific (WP)‐like teleconnection patterns are closely linked to the NPST intensification through the acceleration of the mid‐latitude westerlies. In addition, the strengthening NPST is significantly related to a poleward‐shifted Aleutian Low. In contrast, the low‐frequency variability of the East Asian winter monsoon (EAWM) and tropical sea surface temperature anomalies is not significantly related to the NPST intensification.