It was released as the album's lead single by JYP Entertainment and Republic Records on July 11, 2023.
[1] On June 26, the track listing was released with "Party O'Clock" announced as the lead single.
Park "The AsianSoul", Danke (Lalala Studio), Dr. Jo, Hwang Yu-bin (Verygoods), Wkly, Lee Seu-ran (JamFactory), and Oh Hyun-seo (Lalala Studio), composed by Josefin Glenmark, Paulina "Pau" Cerrilla, Harry Sommerdahl, Fabian "Phat Fabe" Torsson, and J.Y.
[6] It was described as "garage-based" pop song characterized by "bright and exciting melody" with lyrics about "solving the mysterious things that happen in the forest on a midsummer night".
[8] Prior to the release of A Midsummer Nmixx's Dream, on July 11, 2023, Nmixx held a live event on YouTube to introduce the single album and its song, including "Party O'Clock", and to communicate with their fans.