The event, which has only just come to light, occurred off the coast of Brazil at 13:55 GMT on 6 February.
As it burned up, the space rock released the equivalent of 13,000 tonnes of TNT.
This makes it the most powerful event of its kind since an object exploded over Chelyabinsk in Russia in 2013.
That blast was much bigger, releasing the equivalent of 500,000 tonnes of TNT.
More than 1,000 people were injured in that incident on 15 February three years ago, most from flying glass from shattered windows.
But the fireball over the Atlantic probably went unnoticed; it burnt up about 30km above the ocean surface, 1,000km off the Brazilian coast.
Nasa listed the event on its Fireball and Bolide Reports web page.
Measurements suggest that about 30 small asteroids (between 1m and 20m in size) burn up in the Earth's atmosphere every year.
Because most of the Earth's surface is covered by water, most of these fall over the ocean and do not affect populated areas.
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The biggest fireball since the Chelyabinsk explosion has plunged through the atmosphere over the Atlantic Ocean.