[1] "The Happiest Girl" was announced as the sixth track of Born Pink on September 7, 2022, through the group's official social media accounts.
Jeff Benjamin from Billboard ranked "The Happiest Girl" as the second best song on the album for allowing the group to demonstrate their "full-fledged vocal performance."
In particular, he lauded Jisoo's "gorgeous head voice" for shining with a "new vulnerability" as well as Lisa, who usually raps, for showing off her "mature, steady delivery" on the track.
[5] Park Jun-hee of The Korea Herald praised each member's performance on the song, stating that Jisoo and Rosé's falsetto made the song feel "soothing" and left a "deep impression on listeners", while Lisa and Jennie forsook their forte of rapping in order to "tug at people's heartstrings" with their low tones.
[12] Similarly, Vince Ferreras from CNN Philippines complimented the track for highlighting the group's vocals and noted Lisa's performance as its "biggest revelation.
"[10] The Harvard Crimson's Alisa S. Regassa commended Blackpink for stepping outside of their comfort zone and breaking their usual girl crush concept to showcase themselves in a "more raw and authentic light."