His subject matter was wide-ranging and included self-portraits, marines, forest views, portraits, still lifes, airships, dolls and genre scenes.

At the end of January 1904, Spilliaert left Brussels for Paris to try his luck with a publisher or printer of art books.

Watercolor, gouache, pastel, and charcoal—often in combination—were the means by which he produced many of his best works, among which are a number of monochrome self-portraits executed in the early years of the twentieth century.

Spilliaert's expressive use of black finds parallels in the work of Odilon Redon, who was a significant influence.

[3] Frequently depicting a lone figure in a dreamlike space, Spilliaert's paintings convey a sense of melancholy and silence.

Among the best-known works of Léon Spilliaert are the images Digue la nuit and Clair de Lune et Lumières.

In Digue la nuit (1908), the painter removes any naturalistic characteristics of the landscape depicted in the image and creates a stylization in which the location, that serves as a template, is redesigned to become the mirror of a state of mind.

[4] In Clair de Lune et Lumières (c. 1909), the colonnade and arcades of the façade of the Kursaal ballroom on the seawall in Ostend served Spilliaert as a basis for the composition of an urban landscape.

With its cosmic, metaphysical traits Clair de Lune et Lumières reveals the influence of Van Gogh, and is reminiscent of The Starry Night.

His 1903 Self-Portrait with Masks (Musée d'Orsay) is a dramatic self-presentation with ghostly apparitions in the background and a wry face in three-quarter pose.