- 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.
- Megan Fox's last scene was shot 48 hours before the cast & crew attended San Diego Comic Con in 2009.
- Emile Hirsch was considered to play the lead role.
- Matthew McConaughey was considered for a role.
- In an anecdote on "The Tonight Show with Conan O'Brien" (2009), Josh Brolin revealed that he broke and repaired John Malkovich's thumb while shooting a fight scene.
- The sixteenth film released in select D-BOX enabled cinemas, located in the US 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."
- Released on the same day with Toy Story 3 (2010). Director Jimmy Hayward was a former animator of Pixar and worked on the first two Toy Story films.
- Cameo: [Brent Hinds] 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.
- 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.
- Cameo: [gaffer Andy Ryan and cinematographer Mitchell Amundsen] Ryan is the Stunk Crick barber, and Amundsen is the customer he's shaving.