Initially written to include an ironic, tongue-in-cheek tone, Healy was challenged by his co-writers to create a song that was earnest and unabashedly about falling in love.

Using a conventional song structure, the lyrics recount an experience of falling in love, with Healy finding it difficult to express admiration for his partner.

Inspired by the works of actor Buster Keaton and filmmaker Federico Fellini, the black-and-white visual serves as a sequel to the 1975's "A Change of Heart" (2016) and features the band as clowns, with Healy attempting to pursue his love interest from the original video.

[2] The singer told Curto that being a mixed-race couple inspired a couplet in the song that was specific to their relationship: "You show me your Black-girl thing, pretending that I know what it is (I wasn't listening) / I apologize; you meet my eyes / Yeah, it's simple, and it goes like this.

"[3] The line stemmed from her use of culturally-specific, black cosmetic products in their bathroom that Healy was not aware of, which the singer said was an example of conversations about race that occur when living together in a mixed-race relationship.

[9][10][11][12] The song was written by the 1975 members Matty Healy, George Daniel and Adam Hann, while the former two handled the production in collaboration with Jack Antonoff.

[11] Pitchfork's Ryan Dombal found "I'm in Love with You" to be "disarmingly direct",[20] a sentiment shared by Tyler Jenke of Music Feeds, who called it "one of the 1975's most straightforward songs to date" and described the track as being built around a "series of pop hooks and clear-eyed optimism".

[21] Yashavi Upasani of B-Sides said the song acts as a sequel to the 1975's "A Change of Heart" (2016), writing that it "[brings] in the same themes of love despite the lack of understanding within a relationship".

Paolo Ragusa of Consequence said that "I'm in Love with You" is an album highlight; the reviewer commended the "undeniably catchy" chorus and repetitive hook "that begs you not to smile", calling it "one of the most pure and radiantly cheerful songs [that the 1975 has] ever released" and comparing it to "The Sound" (2016).

[29] Katie Rosendale of Local Spins also deemed the song an album highlight,[30] while Callie Ahlgrim of Insider declared it to be one of the best tracks of the 1975's career.

[33] Similarly, Wren Graves of Consequence said the 1975 embraces "their inner poptimists" on the track,[16] and Garro deemed it "perhaps the most accessible distillation of the group’s 1980s-inspired pop experimentation".

[23] Upon the track's debut at the Summer Sonic Festival, Danielle Chelosky of Uproxx commended the "sparkling, jaunty song", highlighting its simplicity and "catchy" melody.

[5] In a separate review following the release of Being Funny in a Foreign Language, Chelosky characterised "I'm in Love with You" as "one of the most charismatic and buoyant" songs on the album, calling the track a "whirlwind of color and wholesomeness" while specifically highlighting the line: "Don’t fuck it, you muppet".

[26] In a mixed review, Chris DeVille of Stereogum compared "I'm in Love with You" to "Happiness" and commended the song's earnestness, declaring it among the most direct of the band's catalogue and saying the track "locks into a groove and leans hard on the simplest of hooks".

[52] In a ranking of the 1975's songs, Molly Marsh of Gigwise placed "I'm in Love with You" at number 45, highlighting the track's "infectious" chorus which she said "carefully skirts the line between catchy and annoying".

[4] In a similar list of the band's work, NME's Rhian Daly ranked "I'm in Love with You" at number 16, characterising it a "pure, unabashed celebration of romance – but with a very 1975 edge".

Daly called the song a rarity amongst the 1975's catalogue, deeming it timeless and sincere while still humorous, specifically the line: "Don't fuck it, you muppet".

[55] Katie Collins, who portrayed Healy's love interest in the "A Change of Heart" video, returned to reprise her role in the visual and also served as the choreographer.

[22][56][57] Upon exiting the tunnel, the singer shows a picture of his love interest from the "A Change of Heart" video to a clown selling vapes, who tells Healy of her location.

[56] The singer eventually finds his love interest, who attempts to strike him with a bowling pin, and the two perform another dance number in which she tries to float away from Healy.

[26][59] Alli Patton of American Songwriter said the "I'm in Love with You" video encapsulated a dreamy and "monochrome harlequin world", praising the cinematography and Healy's dancing.

[22] Rob Ulitski of Promonews praised the cinematography, vintage aesthetic and Collins' performance, calling it a "beautifully made visual" that functioned as a reflection of the 1975 six years after "A Change of Heart".

[21][55] Graves wrote that the visual was charming and praised the choreography, calling it a "kinesthetic wonder", while also comparing Healy's character to Keaton and English comedic actor Charlie Chaplin.

[61] Reviewing the performance, Kress wrote that the singer's straightforward delivery complimented the track's "inherent earnestness" and praised Healy for adding a "unique [and] emotive twist" to each line of the chorus.