Pat's teaching and studies focus on folklore, music, and twentieth-century American literature. He is author of I Heard the Old Fishermen Say: Folklore of the Texas Gulf Coast; Listening to Old Voices: Folklore, Life Stories, and the Elderly; co-author of Lake Erie Fishermen: Work, Identity, and Tradition; The Man Who Adores the Negro: Race and American Folklore; and most recently Right to the Juke Joint: A Personal History of American Music (University of Illinois Press, Urbana, 2018); and articles on folk belief, legend, folk song, gender, and other aspects of American folklore. He is also co-editor of Juneteenth Texas: Essays on African-American Folklore. Dr. Mullen retired from OSU in 2005.

Pat continues to have a very busy schedule in spite of retirement, lecturing and teaching, writing and publishing, cycling and enjoying the great outdoors. He has left a legacy of students who have become accomplished folklorists, working throughout the United States, and a vibrant folklore program at OSU.