It was released on October 18, 2018, as a single from the soundtrack to the 2018 animated film Spider-Man: Into the Spider-Verse,[4] and was later included on Post Malone's third studio album Hollywood's Bleeding (2019).

Malone confirmed his involvement with Spider-Man: Into the Spider-Verse on October 2, 2018, on The Tonight Show Starring Jimmy Fallon, in which he announced that he wrote "Sunflower", which he also performs, and played a snippet of the song.

[5] Spring Aspers, head of music and creative affairs at Sony Pictures, said that "Post and Swae have delivered a song that’s both heroic and emotional, which is exactly what a Spider-Man story needs.

The lyrics are presented in the comic book style of the film, edited into the context of various scenes, such as graffiti scrawled by Miles Morales.

The video contains an exclusive look at the recording session for the song showing the film logo behind Malone and Lee and a live performance.

[12] Israel Daramola from Spin called "Sunflower" a "glitchy, soulful record" that "will appeal to fans of the more melodic songs made by Post and Swae Lee, as they commit to full crooning throughout.

It’s a short and sweet, hazy little pop song that makes sense for a kid’s film or possibly an MTV show about California teens".

[16] Patrick Doyle of Rolling Stone characterized the "hyper-catchy" song as "a diary of a rocky relationship, which walks the line between hip-hop and dream-pop".

"Sunflower" also marks the first Hot 100 number one by two co-billed male leads with no other accompanying acts since George Michael and Elton John's "Don't Let the Sun Go Down on Me" (1992).