Composer John Powell was brought on to collaborate with the rock band Mastodon for the film. However, the film had to undergo re-shoots and re-edits, and Powell had other commitments, so he left and was replaced with Marco Beltrami, whose sensibilities were different and so Mastodon had to collaborate on a completely new score for the film, to their frustration.
During the duration of filming, Josh Brolin could only shave off half his beard to accommodate the prosthetic on the other side of his face. This meant he spent several months walking around with only half a beard on his face.
Thomas Jane showed interest in playing the part of Jonah Hex to the point of having himself photographed in costume complete with special makeup to recreate the character's massive facial scarring. Jane would later lend his voice for the character in an animated short film, DC Showcase Original Shorts Collection (2010).
The sixteenth film released in select D-BOX enabled cinemas, located in the United States and Canada. In D-BOX's words, the motion control technology "adds to the movie's plot and underlying themes of fear, terror and explosive action by offering realistic sensations during most of the film's action scenes."
Megan Fox initially turned down the part of Lilah because in the script incarnation she read, she found it to be too violent and misogynistic. She changed her mind when Josh Brolin came on board and the script was rewritten.
Lilah, Megan Fox's character, refers to her mother as Mrs. Black, and says Lilah is short for Tallulah. Tallulah Black is a character who Jonah Hex helped get revenge on the man who raped and disfigured her. She eventually becomes a bounty hunter and on-again, off-again lover of Hex.
In July 2007, Mark Neveldine and Bryan Taylor were in charge of directing, and had adapted the screenplay too. However, in November 2008 they stepped down from being directors due to creative differences with the studio.
Vocalist and guitarist for progressive metal band Mastodon, makes a cameo appearance during the scene where the train carrying U.S. soldiers comes under attack. Hinds is wearing a U.S. Army uniform and can be seen among the other soldiers. Mastodon, recruited by the film's director Jimmy Hayward, wrote the soundtrack for Jonah Hex.