She was featured alongside Sophie on the song "9 (After Coachella)" by Cashmere Cat, which was the fifth single from his debut album, "9". On 21 April 2017 "Nights with You", the third single from her upcoming second studio album, was officially released worldwide after premiering on MistaJam's BBC Radio 1 show the previous day. On 26 October 2017, MØ released her second extended play, titled "When I Was Young", as a surprise. The EP is composed of songs that MØ wrote over the course of four years since the release of "No Mythologies to Follow". On 30 October 2017, MØ announced a co-headlining North American tour with Cashmere Cat titled the "Meøw Tour" in support of the EP. The tour took place from January to April 2018. In 2017, MØ co-wrote and provided vocals on Diplo's song "Get It Right" for the album "Major Lazer Presents: Give Me Future". They both also performed the song on "The Jimmy Fallon Show" with an appearance from GoldLink. In 2018, MØ collaborated with producer Jack Antonoff to provide vocals for the "Love, Simon" soundtrack with the song "Never Fall in Love". She also collaborated with Noah Cyrus on the song “We Are...” and was featured on Alma's mixtape "Heavy Rules" with the song "Dance for Me". On 19 October 2018, MØ released her second studio album, "Forever Neverland," by Columbia Records. The album was preceded by eight singles: "Nostalgia", "Sun in Our Eyes" featuring Diplo, "Way Down", "Imaginary Friend", "Blur" featuring Foster the People, “Beautiful Wreck”, “Purple Like the Summer Rain” and “I Want You”. The album also features collaborations with Charli XCX, What So Not, Two Feet and Empress Of. She revealed that other singles "Kamikaze", "Final Song" and "Nights with You" will only be available on the Japanese edition of the album. In 2019, MØ performed her single "Blur" on "The Tonight Show Starring Jimmy Fallon,"  she co-wrote and provided vocals to the theme song for "Moominvalley", and was the support act for Panic! at the Disco's tour across the United Kingdom. MØ performed at 2019’s Glastonbury Festival and Roskilde Festival.