Johnson graduated from Bowling Green State University in Bowling Green, Ohio with a bachelor of arts degree in economics before attending law school at Capital University in Columbus where he received his Juris Doctor degree in 1985. While at Bowling Green, he became a member of Delta Tau Delta International Fraternity. He was admitted to the Ohio bar on November 4, 1985. After a year as an assistant city prosecutor in Columbus, he joined the firm of Chester, Willcox, and Saxbe in Columbus working there until 2001.