The film's origins trace back to a 1993 episode of Dr. Quinn, Medicine Woman, on which Johnny Cash was a guest star and befriended star Jane Seymour and her ex-husband, director James Keach.

By the mid-1990s, Cash had asked Keach to make a biopic of his life, and the project's script went through years of development, being turned down by Sony and other studios before Fox 2000 Pictures agreed to make it.

Russell Crowe was offered the role of Johnny Cash but turned it down because it felt wrong to him, a decision he later came to regret.

Joaquin Phoenix had actually met Johnny Cash months before hearing about the film project, and upon reading the script he initially felt at least ten other actors would be better suited for the role.

Both Johnny and June Carter Cash personally approved the casting of Joaquin Phoenix and Reese Witherspoon in 2003, before their deaths.

Joaquin Phoenix performed all of Cash's vocal tracks himself for both the film and its soundtrack, and worked with a voice coach to lower his voice by an octave.

Reese Witherspoon was surprised to learn she would have to sing her own vocals as June Carter, and prepared by studying videos of Carter performing and telling stories; she found learning to play the autoharp even harder than the singing.

Witherspoon experienced severe stage fright and physical illness before shooting her first live performance scene in front of extras.

Walk the Line became the all-time highest-grossing music biopic until Straight Outta Compton surpassed it in 2015.

The 2005 TV movie Elvis, which also features actor Robert Patrick (playing Elvis Presley's father instead of Cash's), is considered an unofficial companion piece to Walk the Line, as both begin and end in 1968 with concert performances by their respective subjects.

Walk Hard: The Dewey Cox Story, a 2007 comedy starring John C. Reilly, serves as a direct parody of Walk the Line and the musical biopic genre as a whole.