The seasonal heat transport mechanisms important in the Pacific equatorial upwelling zone are investigated using the primitive equation, reduced gravity model developed by Gent and Cane. Mechanisms of meridional heat transport are shown and discussed with respect to the heat budget of a box about the equator containing the upwelling. There is a horizontal cell in which warm water enters the upwelling box in the west in strong equatorward currents located near the western boundary, which feed the eastward flowing undercurrent. To compensate, water leaves the section as a colder and weaker poleward thermocline flow in the eastern basin. The meridional-vertical cell comprises additional equatorward geostrophically balanced inflow in the upper thermocline, which is compensated by the warmer poleward outflow by Ekman divergence in the surface layer.