Redden, then 15, earned his role in Deliverance during a casting call at Clayton Elementary School in Clayton, Georgia. To add authenticity and humor to the film, the filmmakers found Redden to fit the look of the inbred and intellectually disabled banjo boy called for by the book, although Redden himself is neither. His distinctive look was enhanced using special makeup.
In his famous scene, Redden plays the instrumental "Dueling Banjos" opposite actor Ronny Cox on guitar. It is noted for foreshadowing the film's theme: exploring unknown and potentially dangerous territory. Redden could not actually play the banjo. A local musician, Mike Addis, reached around from behind Redden; this was disguised using careful camera angles.
Redden also appeared in Tim Burton's 2003 film Big Fish. Burton was intent on getting Redden, who hadn't appeared in a film since Deliverance, to play the role of a banjo-playing welcomer in the utopian town of Spectre. Burton eventually found him in Clayton, Georgia, where he worked as a cook, dishwasher, and part-owner of the Cookie Jar Café.
In 2004, Redden made a guest appearance on Blue Collar TV playing an inbred car repairman named Ray in a "Redneck Dictionary" skit, for the word "raisin bread" (as in "Ray's inbred"). He played a banjo in the skit.
In 2012, Redden was featured on an APM Marketplace piece on the feelings of people in Rabun County about Deliverance 40 years after the film's release. He said that though Deliverance was the best thing that happened to him, he never saw much money from the movie. "I’d like to have all the money I thought I’d make from this movie. I wouldn’t be working at Walmart right now. And I’m struggling really hard to make ends meet."  Redden went on to explain that the people in Rabun County were good people, and that the stereotypes about them that many took away from the movie were not true: "We’re not a bad people up here, we’re a loving people. Rabun County is a pretty good town. It’s peaceful, not a lot of crime going on, just a real peaceful town. Everybody pretty much gets along with everybody." 
- Billy Redden at the Internet Movie Database
- Blake Spurney (News Editor) (October 7, 2004). "Another celebrity appearance for Rabun star (Archived 27 Dec 2004)".