A novelist, short story writer, and art critic he was also educated in law.

His use of symbolism and mastery of ambience sets his novels apart from earlier romance pieces.

This movement was influential in raising the national consciousness of Belgians, ushering in modernism and discouraging romanticism.

Demolder contributed to La Jeune Belgique as an art critic and published an early monograph on symbolist artist, James Ensor in 1892.

He married Claire Dulac-Rops, the daughter of the Belgian illustrator and artist Félicien Rops.