O'Neill will be a contributor to the news channel and "offer military expertise and analysis across various daytime and primetime programs," said a statement from the channel, a unit of Rupert Murdoch's 21st Century Fox.
In a Fox documentary last year, O'Neill was said to have killed bin Laden in a secret US military operation in Pakistan.
Ahead of the documentary's airing, O'Neill told The Washington Post that he fired the fatal shot that hit the Al-Qaeda leader at his hideout in the Pakistani garrison city of Abbottabad in May 2011.
He has received more than 52 military decorations, according to the Fox statement.
"Rob O'Neill is an American hero who dedicated his life to serving our country and protecting our freedoms," said Fox News chairman and chief executive Roger Ailes.
"It's incredibly rare to have someone in a television contributor role with his leadership experience and expertise at the fighting unit level. His military insight will be a major asset to the network and we are honored to have him.