Using observations and Atlantic forced coupled model simulations, we show evidence for an asymmetry in the link between beginning of year tropical Atlantic sea surface temperature anomalies (SSTAs) and end of the year El Niño‐Southern Oscillation events. We find a greater tendency for warm Atlantic SSTAs to lead to a La Niña than for cold anomalies to lead to El Niño. The model experiments showed that the Atlantic had a greater chance to force the tropical Pacific if the Pacific was initially in a neutral state. In the model, a warm Atlantic from March–May was able to produce an atmospheric response leading to easterly wind anomalies in the western Pacific. This in turn induces a subsurface oceanic response, leading to La Niña at the end of the year. The atmospheric response does not occur for a cold Atlantic, leading to no impacts in the Pacific. Plain Language Summary: It has been found that the tropical Atlantic can have an impact on an El Niño or La Niña events that form in the tropical Pacific at the end of the year. We show using observations and targeted model experiments that a warmer than normal Atlantic from March‐May can lead to a La Niña, but a colder than normal Atlantic does not lead to an El Niño. The model shows a strong atmospheric response to warm Atlantic surface temperature, leading to wind changes in the Pacific that aid La Niña formation. This strong atmospheric response does not occur for cold Atlantic temperatures leading to no changes in the Pacific. The model also shows that the Atlantic has a greater chance of impacting the Pacific at the end of the year if the Pacific is already in near average conditions at the beginning of the year. These results may improve forecasts of La Niña events and may help in understanding past changes in the Atlantic‐Pacific relationship. Key Points: Observed tropical Atlantic forced pacemaker experiments produce La Niña events, but not El Niño events, in unison with observationsA warm Atlantic had a greater chance of leading to a La Niña event if the tropical Pacific was initially in neutral conditionsThere was a tropical‐wide response to a warm Atlantic in the model, affecting western Pacific wind. This was not seen for a cold Atlantic [ABSTRACT FROM AUTHOR]