<p>Self-sustained multicentennial variability of the Atlantic Meridional Overturning Circulation (AMOC) has been previously demonstrated in one‐hemisphere box models. In this study, we extend our earlier work by developing a two‐hemisphere box model that incorporates both thermohaline and wind‐driven components. Our analysis reveals that a robust, weakly damped multicentennial eigenmode persists in the two‐hemisphere framework, with the salinity advection feedback in the North Atlantic remaining the dominant control mechanism, while the South Atlantic plays a minor role. Compared to the one‐hemisphere model, the self-sustained multicentennial oscillation in the two-hemisphere box model is much easier to occur and less sensitive to changes in basin geometry. A further simplified box model is developed to reproduce the key eigenmode of the original model. This simplified model provides analytical insights showing that the oscillation period is primarily controlled by basin geometry and mean AMOC strength. Moreover, the inclusion of wind‐driven circulation acts to weaken the oscillation amplitude, with negligible impact on the oscillation period. Finally, we further demonstrate that the thermohaline component of the AMOC is a necessary and sufficient condition for the multicentennial oscillation in this model, as the shallow wind-driven overturning cannot exhibit multicentennial oscillations. Overall, these findings demonstrate the robustness of multicentennial AMOC oscillations and clarify the essential role of thermohaline processes in shaping their dynamics across varying oceanic configurations.</p>