His works were translated, published, and performed in England, France, Germany, and Sweden during his lifetime, in addition to his native Denmark.

he wrote the libretto for August Enna's opera Aucasin og Nicolette, which was performed at the Royal Danish Theatre.

In 1898 he wrote the libretto for an opera titled Portia in collaboration with Carl Nielsen, which was based on William Shakespeare's The Merchant of Venice.

He published a translation of Gustave Flaubert's Salammbô in 1902, and The Temptation of Saint Anthony (Danish: Den hellige Antonios Fristelser) in 1904.

[3] In addition to his work as a translator, reviewer, and lyricist, Michaëlis authored several original novels.

His 1912 novel, The Eternal Sleep (Danish: Den evige søvn) described Napoleon's march into Russia and his eventual defeat there.