US District Court Judge Timothy Kelly, an appointee of the president, announced his decision on Friday.
Mr Kelly said Mr Acosta's credentials would be returned immediately and reactivated to allow him access to the White House.
The journalist was accused of "unacceptable" conduct during a heated news conference with Donald Trump after the midterm elections.
Press secretary Sarah Sanders took aim at him for "placing his hands on a young woman just trying to do her job as a White House intern".
The network's chief White House correspondent has clashed repeatedly with Mr Trump and Ms Sanders in briefings over the last two years.