Upon release, Harlequin received mostly positive reviews from music critics, who praised Gaga's syncretic interpretation of Harley Quinn and the Great American Songbook but felt the album was not much of a creative departure from her works with Bennett.

Following the completion of The Chromatica Ball (2022), Lady Gaga took a step back from social media and promotional activities while she focused on preparing her role as Harleen "Lee" Quinzel (Harley Quinn) in the American musical thriller film Joker: Folie à Deux (2024).

[2] Throughout the rest of the year and into 2024, she occasionally teased upcoming music via social media, sharing photos from within the studios where she was working and offering insights into the process.

[3] At the film's red carpet premiere in London, England, on September 25, 2024, Gaga discussed the inspiration for the album, stated, "When we were done with the movie, I wasn't done with her.

Gaga also reflected on her artistic choices, stating, "In a funny way, if I had put rock & roll chords over production in a record that I did with Tony years ago, I don't know how he would've felt about that.

[10] She later uploaded four more "cryptic" images with three containing sound through Instagram, with many fans believing to be her seventh studio album or related to Joker: Folie à Deux.

[15] The album's standard cover features Gaga standing in a shower sporting orange hair while wearing a white clothed-dress with a flotation device around her neck.

[16] An alternate cover used for an exclusive vinyl sold only on Gaga's web store shows her in a messy bedroom lying on the bed facing the ceiling.

[17] The back cover of the album features a photograph of a messy bedroom with the 1862 painting Stańczyk by the Polish painter Jan Matejko hanging on the wall.

Rolling Stone's Rob Sheffield,[28] Sputnikmusic's Dakota West Foss,[30] Tony Clayton-Lea of The Irish Times,[27] and Consequence's Mary Siroky complimented the album's musical style, boldness, and Gaga's passionate rendition of the jazz standards.

"[23] Sal Cinquemani of Slant Magazine and Melissa Ruggieri of USA Today regarded Harlequin as an album demonstrating Gaga's vocal prowess.

[24][33] Michael Cragg for The Guardian thought Harlequin as a product of Gaga's Jazz & Piano concert residency whilst channeling Harley Quinn's different moods, but regarded it as a prelude rather than a fully-conceived record.