As a graduate student, Lentz served as a teaching fellow at Vanderbilt University between 1964 and 1969. In 1969, he returned to Kenyon College, where he has spent his entire career, being appointed assistant professor of English in 1969, associate professor in 1973, and then full professor. He was subsequently appointed to an academic chair, McIlvaine Professor of English, and has served as chairman of the English Department.
In honor of his distinguished tenure and teaching excellence, Kenyon College opened the Lentz House for its Department of English in 2009. Lending his name to the new English building places Lentz in the ranks of other highly distinguished Kenyon faculty, such as John Crowe Ransom, for whom Ransom Hall, Kenyon's Admissions building, was renamed in 1958.