Using a dynamically motivated analysis of observations, and an intermediate-level coupled model, the interannual variability within the equatorial Atlantic is studied. It is found that a significant part of the observed variability can be described by an equatorial coupled mode akin to ENSO (El Niño–Southern Oscillation). The Atlantic mode signature is even more tightly focused on the equator and is situated proportionally farther to the west within the basin than its Pacific counterpart. Model simulations capture the equatorial coupled mode in relatively pure form and, for what are thought to be the most realistic parameter choices, show interannual oscillations favoring a 4-year period, which are not self-sustaining. The simulated spatial patterns agree well with those extracted from observations, including those features that distinguish the Atlantic from the Pacific. Sensitivity experiments show that the Atlantic coupled-mode signal is less robust than the corresponding Pacific ENSO signal bu... Abstract Using a dynamically motivated analysis of observations, and an intermediate-level coupled model, the interannual variability within the equatorial Atlantic is studied. It is found that a significant part of the observed variability can be described by an equatorial coupled mode akin to ENSO (El Niño–Southern Oscillation). The Atlantic mode signature is even more tightly focused on the equator and is situated proportionally farther to the west within the basin than its Pacific counterpart. Model simulations capture the equatorial coupled mode in relatively pure form and, for what are thought to be the most realistic parameter choices, show interannual oscillations favoring a 4-year period, which are not self-sustaining. The simulated spatial patterns agree well with those extracted from observations, including those features that distinguish the Atlantic from the Pacific. Sensitivity experiments show that the Atlantic coupled-mode signal is less robust than the corresponding Pacific ENSO signal bu...