In October 2014, 20th Century Fox revealed that Christophe Beck would score the film. Beck stated, "With the Peanuts movies, I grew up on those specials from the '60s and '70s, that, of course, rerun to this day. I'm very fond of all that Vince Guaraldi music, so what we did was try to find spots in the film where we could sort of touch down and remind people who were watching the film that it's still a Peanuts movie, and there's still a place for that music in the film. There's a bunch of spots where we quote the Guaraldi music, or we actually re-record his pieces quite faithfully." He also added that the score would be more orchestral than Guaraldi's previous scores, which were mainly a small jazz combo. Jazz pianist David Benoit contributed to Beck's score. On July 28, 2015, Fox announced that American singer-songwriter Meghan Trainor was writing and performing an original song for the film, titled "Better When I'm Dancin'". About the song, Trainor stated that "They wanted a song about confidence and knew I was good at writing those. I feel better when I’m onstage dancing and having fun, so I wrote about that!”
"Better When I'm Dancin'" by Meghan Trainor was released as a promotional single from the soundtrack on October 13, 2015. The song, which is a tropical track, strays from Trainor's usual musical style, being described as "breezy and harmless" with traces of house music.