It began serialization online in February 2016 on the user-generated novel publishing website Shōsetsuka ni Narō.

A manga adaptation with art by Anajiro has been serialized online via Futabasha's Gaugau Monster website since July 2019 and has been collected in eleven tankōbon volumes.

Written by Ryousuke Hata, The Strongest Magician in the Demon Lord's Army Was a Human began serialization online on the user-generated novel publishing website Shōsetsuka ni Narō on February 22, 2016.

[6] It was later acquired by Futabasha who published five volumes with illustrations by Kuma from September 30, 2016, to April 27, 2018, under their Monster Bunko light novel imprint.

It was produced by Studio A-Cat and directed by Norihiko Nagahama, with Touko Machida writing series scripts, Masami Sueoka designing the characters, and Kohta Yamamoto composing the music.