Johnson has made important contributions in the fields of performance studies, critical race theory, and queer theory (especially queer of color critique). He is currently Chair of the Department of Performance Studies at Northwestern University, where he is also a member of the core faculty in the Department of African American Studies. Before going to Northwestern, Johnson was an Assistant Professor of English at Amherst College in Amherst, Massachusetts. As a performance artist, Johnson has toured his one-man show, Strange Fruit, around the United States since 1999. He performed his oral history and published book, Sweet Tea: Black Gay Men of the South, as part of About Face Theatre's 2009-10 season.
Johnson's first book, Appropriating Blackness: Performance and the Politics of Authenticity was an important study of how "blackness" was "performed" and contested in different social contexts, particularly in relationship to gender and sexuality. The book won several awards, including the Lilla A. Heston Award, the Errol Hill Book Award, and was a finalist for the Hurston/Wright Legacy Award. His co-edited book Black Queer Studies: A Critical Anthology was an important collection of essays by prominent scholars in African American and Queer studies, based on a conference Johnson co-organized at the University of Chapel Hill in 2000. His most recent work is an oral history of black gay men in the southern United States entitled Sweet Tea: Black Gay Men of the South, published by the University of North Carolina Press.