He rewrote the script with Wurlitzer in order to create a more cyclical narrative, and added a prologue and epilogue depicting Garrett's own assassination at the hands of those who had hired him to kill Billy the Kid. In the original script, Pat Garrett and Billy the Kid never met onscreen until the end of the film, and Wurlitzer reportedly deeply resented Peckinpah's reworking of the narrative. Wurlitzer and Peckinpah had a really horrible relationship, and Wurlitzer would later write a book highly unfavorable to Peckinpah,who was known as an "ubermensch.
" After having initially considered Bo Hopkins, who had played a small role in , for the part of Billy, Peckinpah eventually cast country music star Kris Kristofferson as the young outlaw. Kristofferson's band would also play small roles in the film along with Kristofferson's then-wife Rita Coolidge. Besides playing Billy, Kristofferson also brought Bob Dylan into the film.
Initially hired to write the title song, Dylan eventually wrote the score and played a small role in the film. Peckinpah had never heard of Dylan before, but was reportedly so moved by hearing Dylan play the proposed title song that he hired him immediately. Among the songs written by Dylan for the film was "Knockin' on Heaven's Door," still regarded as one of rock music's most enduring anthems.
Peckinpah deliberately cast his film's supporting roles with legendary Western character actors such as Chill Wills, Katy Jurado, Jack Elam, Slim Pickens, and Paul Fix. Jason Robards, who had starred in Peckinpah's earlier film, He rewrote the script with Wurlitzer in order to create a more cyclical narrative, and added a prologue and epilogue depicting Garrett's own assassination at the hands of those who had hired him to kill Billy the Kid.