This study examines the basin-wide adjustment process associated with El Ni¿o-Southern Oscillation (ENSO) in terms of oceanic waves using the Cane-Zebiak model. The Rossby waves induce not only the meridional mass divergence in the ocean interior but also the incoming zonal mass flux at the western boundary, which generally overcompensates the interior meridional divergence. Therefore, the Rossby waves alone cannot make a negative feedback. However, the outgoing zonal mass flux associated with the reflected Kelvin wave at the western boundary reduces the incoming boundary mass flux associated with the Rossby waves, resulting in the tendency of equatorial basin-wide heat content varying in phase with the meridional divergence. Also shown is that the nonequilibrium adjustment of the tropical Pacific Ocean is mainly due to the free Kelvin waves reflected at the western boundary. ¿ 2001 American Geophysical Union