Hataraku Maō-sama! began as a light novel series written by Satoshi Wagahara, with illustrations by the artist Oniku. Wagahara originally entered the first novel in the series with the title Maōjō wa Rokujō Hitoma! (魔王城は六畳一間! Demon Castle within a six-tatami room!) into ASCII Media Works 17th Dengeki Novel Prize in 2010, where the novel won the Silver Prize. The first novel was published by ASCII Media Works on February 10, 2011 under their Dengeki Bunko imprint, and eightteen volumes have been released as of January 2018, as well as two Volume backstories.
Yen Press has announced that they have licensed the light novels in English. The first volume was released on April 21, 2015.