The name Nmixx combines the letter "N", which stands for "now", "new", "next", and the unknown "n", and the word "mix", which symbolizes combination and diversity, altogether meaning "the best combination for a new era".

On July 9, 2021, JYP Entertainment announced a new girl group would be debuting in February 2022, its first since Itzy in 2019. From July 16 to 25, JYP Entertainment made pre-orders available for a limited edition of the group's debut package, titled Blind Package, which included the group's debut album and album-related materials. The members were revealed through various dance videos and song covers from August 6 to November 19 (in order: Jinni, Jiwoo, Kyujin, Sullyoon, Bae, Haewon, and Lily).

On January 26, 2022, JYP Entertainment announced the group's name to be Nmixx, until then tentatively called JYPn. On February 2, it was announced that they would debut on February 22 with the release of Ad Mare. On February 18, 2022, JYP Entertainment announced that the group's debut showcase, originally scheduled for February 22, would be postponed to March 1 after group member Bae tested positive for COVID-19. Nmixx collaborated with the DreamWorks Animation's Gabby's Dollhouse to release the Korean version of "Hey Gabby!", alongside the B-side "Sprinkle Party", on May 2. They also participated in Project Ribbon's Summer Vacation Project, along with Fromis 9 and Oh My Girl Banhana, to cover Rainbow's "Kiss", from their 2009 debut EP Gossip Girl. The song was released on July 31.

On September 19, Nmixx released their second single album Entwurf alongside the lead single "Dice". The group released their first "Intermixxion" single (described by JYP as a special track dropped as a standalone track inbetween official releases) and first Christmas song, "Funky Glitter Christmas", on November 23. On December 9, JYP Entertainment announced that Jinni had terminated her contract with the company due to personal reasons, and had departed from the group, while Nmixx would continue as a six-member ensemble.

On March 20, 2023, Nmixx released their first extended play Expérgo, with the title track "Love Me Like This". They embarked on the Nice to Mixx You Showcase Tour, consisting of 13 dates across the United States and Asia, beginning in May. On May 31, it was reported that JYP Entertainment has expanded their partnership with Republic Records to include Nmixx, along with Xdinary Heroes, in their strategic label deal, which previously included Twice, Itzy and Stray Kids. On July 11, 2023, Nmixx released their third single album A Midsummer Nmixx's Dream, which consists of four tracks, including the pre-release track "Roller Coaster", and the title track "Party O'Clock" written and composed by J. Y. Park. On August 20, JYP Entertainment announced that Nmixx would be holding their first fan concert Nmixx Change Up: Mixx University, on October 7 and 8 at the Jangchung Arena in Seoul. The group went on to hold the fan concert abroad at Hong Kong, Taipei and Macau in 2024.

On January 15, 2024, Nmixx released their second extended play Fe3O4: Break, with the pre-release track "Soñar (Breaker)" and the title track "Dash". On July 17, JYP Entertainment announced that the group would be holding their second fan concert Nmixx Change Up: Mixx Lab, from October 4 to 6 at the Jangchung Arena in Seoul. Nmixx's third extended play Fe3O4: Stick Out was released on August 19, with the title track "See That?". On October 11, the group released the Spanish version of "Soñar".