Cordero made his Reds debut on March 31, 2008, pitching an inning in a 4–2 loss to the Arizona Diamondbacks at Great American Ballpark. Cordero earned his first save as a Red on April 3, 2008, pitching a scoreless ninth inning in a 3–2 win over Arizona. On April 5, 2008, Cordero earned his first victory with Cincinnati, getting the decision in a 4–3 win over the Philadelphia Phillies. He finished the 2008 season with a 5–4 record and a 3.33 ERA in 72 games pitched, earning 34 saves.