This song was written by Roxette's instrumentalist Per Gessle. In a March 2011 interview with the London commuter freesheet Metro, he was asked how many times Roxette had performed "It Must Have Been Love," to which he replied:

"We've done it at every show, so it's been hundreds of times. We don't need to rehearse it, put it that way. It's the same with 'Listen To Your Heart' or 'The Look' – when you stand there in front of 10,000 who love it, it's an amazing feeling."

Asked further, "Have you heard your songs in any unlikely places?," he said of the same song: "I was in Siberia the other day and heard a balalaikan version of 'It Must Have Been Love.'"

Originally called "It Must Have Been Love (Christmas For The Broken Hearted)," the song was released as a single backed by "Turn to Me." At the time, Roxette was doing promotion in Germany and was having a hard time getting on the radio because they fell between the Top 40 and rock formats. EMI's German division suggested the duo record a Christmas tune to try to get some airplay, so Gessle got to work writing a holiday ballad. It still didn't make German radio (at least not the original version; the re-release hit #4) but became a big hit in the duo's native Sweden in 1987. >>

Recorded before Roxette started working on their Joyride album, "It Must Have Been Love" was reworked for the movie Pretty Woman, starring Julia Roberts and Richard Gere. The movie was an enormous hit, and so was the soundtrack, which also featured "King Of Wishful Thinking" by Go West. Released in March 1990, Pretty Woman developed a huge following, which helped send this song to the top of the US Hot 100 in June, where it stayed for two weeks.

For the Pretty Woman version, Gessle kept most of Marie Fredrikkson's original vocals but cut out the Christmas sounds at the beginning of the song. He also changed the lyric "a hard Christmas day" to "a hard winter's day."

According to Gessle, Pretty Woman director Garry Marshall loved the song so much he re-edited the movie so he could showcase it in a scene without dialogue. Still, Gessle, who had never had a song placed in a film before, was initially disappointed when only about a minute of it was used. He told Billboard he thought, "Everything is going to circle around my song."

But there were no complaints when the movie and song became instant hits. "Nobody expected the movie to become such a smash and for us it was, of course, a jackpot," he told Songwriter Universe in 2018.

This was used on the Canadian TV series Being Erica in the 2009 episode "Dr. Tom." It was also used in the 2013 Swedish film Hotel, starring Alicia Vikander, and the 2013 romantic comedy Austenland, starring Keri Russell.