The two-time presidential candidate, known for his staunch antiwar and gun-control voting record -- receiving an "F" grade from the National Rifle Association -- signed a multiyear paid deal with the network, Fox said in a statement.
He will appear on both Fox News Channel and Fox Business Network, said Fox, which calls itself "Fair and Balanced" but critics say promotes conservative political positions.
"Through 16 years in Congress and two presidential campaigns, Fox News has always provided me with an opportunity to share my perspective with its enormous viewership," Kucinich said in a statement. "I look forward to a continuation of our relationship this time as a Fox News contributor."
Kucinich is a former Democratic lawmaker who lost his Ohio House seat after eight terms last year and left office Jan. 3.
Fox News Chairman and Chief Executive Officer Roger Ailes praised Kucinich.
"I've always been impressed with Representative Kucinich's fearlessness and thoughtfulness about important issues," he said in a statement.
"His willingness to take a stand from his point of view makes him a valuable voice in our country's debate," said Ailes, a former media consultant for Republican Presidents Richard Nixon, Ronald Reagan and George H.W. Bush.
Kucinich tried to impeach President George W. Bush and Vice President Dick Cheney for allegedly manufacturing evidence to sway U.S. public opinion in favor of 2003's U.S.-led invasion of Iraq. He sued President Barack Obama in federal court over whether Obama illegally skirted Congress when he approved 2011's U.S. military action in Libya.