We examined decadal variability of the Subtropical Front (STF) of the western North Pacific by using a North Pacific ocean general circulation model (OGCM), comparing the results of three simulations with different horizontal resolutions. In the long-term mean fields, the eddy-resolving model (10 km) was able to simulate the distributions of the STF and the associated Subtropical Countercurrent (STCC) between 20°N and 30°N better than either the non-eddy-resolving model (100 km) or the eddy-permitting model (20 km) because it simulated the Kuroshio recirculation gyre more realistically. The simulated STF intensity exhibited significant decadal-scale variations: it was stronger in the late 1970s and weaker in the early 1990s. During these two periods, the simulated mode waters showed corresponding differences in their potential vorticity minima density and paths. We also investigated the relationship between the decadal-scale STF variability and atmospheric forcing. The results suggest that the decadal-scale STF variability can be largely explained by changes in the mode waters formed in the western North Pacific and advected to north of the STF by the subtropical gyre in response to a change in surface westerly winds that occurred in the mid-1970s.