Dennard attended Michigan State University between 2010 to 2013. As a true freshman in 2010, Dennard played in six games with two starts. He missed five games due to injury. As a sophomore in 2011, he played in 11 games, missing two due to injury. He finished the season with 42 tackles and three interceptions, two which came against Georgia in the Outback Bowl. As a junior in 2012, he started all 13 games, recording 52 tackles and three interceptions. He was a first team All-Big Ten selection. As a senior, he won the Jim Thorpe Award.
Dennard was selected by the Cincinnati Bengals as the 24th pick of the first round. He signed a four-year, $8 million contract with $6.5 million guaranteed with the Bengals on June 12, 2014.