It was thought there was a one-in-200,000 chance that it could strike on 13 April 2036, but revised calculations have now ruled this out.
Instead, Nasa scientists said it would not get closer than 31,000km as it flies past on this date.
They were able to study the rocky mass as it made a relatively close approach above our planet, allowing them to better assess its future threat.
"Radar data we have collected over the past couple of weeks have completely excluded any chance of impact in 2036.  Furthermore, we can now precisely predict its trajectory decades into the future," Marina Brozovic of the Nasa's Jet Propulsion Laboratory told the BBC Stargazing Live programme.
The Apophis asteroid is named after the Egyptian demon of destruction and darkness.
Hazardous asteroids
It caused alarm after it was discovered in 2004, when scientists thought it could have a one-in-45 chance of smashing into the Earth in 2029.
Improved calculations later lifted this threat, but until this week, the very tiny but real chance of a hit in 2036 remained.
If an asteroid of this size did smash into Earth, it would strike with the energy of about 100 of our largest nuclear bombs.
But for now, this has been ruled out - at least for Apophis.
Scientists are becoming increasingly interested in potentially hazardous asteroids.
So far, they have catalogued more than 9,000 of them, and spot on average another 800 new ones each year.
One recent discovery is 2012 DA14. On 15 February, this rock, which measures about 45m in diameter, will pass about 36,000km from the Earth.
This is closer to the Earth than some satellites, but again scientists say there is no chance of a collision.
2012 DA14 should be visible with binoculars or small telescopes.
A 300m-wide asteroid will not hit the Earth in 2036, US astronomers say.