On February 6, 2007, Harang signed a four-year, $36.5 million contract with the Cincinnati Reds.
On July 23, 2007, Harang threw ten innings for the Reds (throwing 121 pitches), becoming the first Reds pitcher to do so since 1989. However, he received a no-decision because the Reds did not win the game until the 12th inning.
On September 3, 2007, he became the 3,000th strikeout recorded by the New York Mets' Pedro Martínez.