The song was written by Joe Newman, Gus Unger-Hamiltion, and Thom Sonny Green and produced by Charlie Andrew.

The song's title is based on a game the band played where they asked the question, "What historical figure would I want to take on a date if she were alive today?

Thus the first verse is about Lee Miller, Joe's deadcrush, the second about Anne Boleyn, Gus's.A music video for the song was released on 12 July 2017.

[4] It features the band's "dead crushes": Sylvia Plath, Lee Miller, and Anne Boleyn teaming up in a post-apocalyptic world.

Four remixes of "Deadcrush", by Spike Stent, Ben de Vries, Lea Porcelain, and Salute, were individually released by Alt-J as digital singles in August 2017.