M. Night Shyamalan conceived the film's structure to mirror a comic book's traditional three-part story arc (birth, struggles, and final battle with an archenemy), but found the origin/birth section most compelling and decided to focus the entire film on it.

Shyamalan approached Bruce Willis for the lead role during the filming of The Sixth Sense, and wrote Unbreakable as a spec script with both Willis and Samuel L. Jackson already in mind for the two leads.

Samuel L. Jackson recalled learning about the script from Willis himself during a chance meeting in a casino in Casablanca, shortly after Willis had finished filming The Sixth Sense.

Julianne Moore was originally cast as Audrey Dunn in January 2000 but dropped out two months later to play Clarice Starling in Hannibal, and was replaced by Robin Wright.

Following the success of The Sixth Sense, Disney purchased Shyamalan's Unbreakable screenplay for a spec-script record of $5 million, plus another $5 million for him to direct, and the deal helped him launch his own production company, Blinding Edge Pictures.

Principal photography ran from April 25 to July 2000, shot mostly on location in Philadelphia, the film's actual setting.

Samuel L. Jackson personally requested that Mr. Glass's cane be made of glass to make the character more menacing, and he also suggested using purple as Elijah's signature color to contrast with David Dunn's green.

Elijah's wig as Mr. Glass was modeled after abolitionist and statesman Frederick Douglass.

Comic book writer Kevin Smith noted that Unbreakable bore brief similarities to the graphic novel Mage: The Hero Discovered by Matt Wagner.

M. Night Shyamalan makes a cameo as the Stadium Drug Dealer, a role he later reprised as a security guard named Jai in both Split and Glass.

In October 2018, Shyamalan confirmed a long-standing fan theory that the unnamed five-year-old boy and woman who bump into David Dunn near the stadium are younger versions of Kevin Wendell Crumb and his mother Penelope, characters later central to Split.

Despite a mixed critical and box-office reception at release that disappointed Shyamalan, Unbreakable later gained a strong cult following and was ranked by Time in 2011 as the fourth-best superhero film of all time.

Quentin Tarantino included Unbreakable on his list of the top 20 films released between 1992 and 2009, calling it a brilliant retelling of the Superman mythology and praising it as Bruce Willis's best performance.

More than 15 minutes of footage were cut from the film during post-production, and these deleted scenes were later included on the DVD release.

Composer James Newton Howard, fresh off scoring The Sixth Sense, recorded the Unbreakable score at AIR Studios Lyndhurst Hall, a converted church in London.