"I promise I won't let you down and I promise I will stand strong as we take back our country," said Kinzinger. "Thank you for taking back the 11th congressional district."
Kinzinger, 34, received 57 percent of the vote with 100 percent of precincts reporting.
Kinzinger is an Air Force pilot who has received support from Tea Party activists and Sarah Palin.
The 11th district was traditionally Republican until Halvorson, a former state senator, won the term in 2008.
"Even though these weren't the results we had hoped for, we're going to wake up and help people tomorrow, and the day after that," said Halvorson in her concession speech.