The space rock, 2012 EG5, flew past earth closer than the moon, at a distance of just 143,000 miles.
The asteroid has a diameter of around 150 feet - and would have exploded with the force of an atomic weapon had it hit our planet.
Nothing is known about its likely composition. The asteroid flew past Earth on Sunday at 9.32am GMT.
An impact with an asteroid of that size would not cause a planet-wide disaster similar to the one that wiped out the dinosaurs 65 million years ago - but would hit Earth's surface and explode.
The asteroid was spotted by the Pan-STARRS 1 telescope in Hawaii on March 13 this year.
'Asteroid 2012 EG5 will safely pass Earth on April 1,' said scientists at Nasa's Jet Propulsion Laboratory via a Twitter post. Read More