The tree sits on the ruins of the towers, still being cleared by workers, and is topped with an American flag as well thousands of angels with the names of those killed.
The tree-lighting ceremony was the idea of construction worker Jimmy Nolan. He hopes it will cheer up workers still trying to clear the rubble.
The Twin Towers of the World Trade Centre collapsed, killing more that 3,000 people, when two hijacked planes slammed into them.
As well as the thousands in the Twin Towers, the collapse also took the lives of hundreds of rescue workers who had rushed to the tragic scene.