He was an adherent of the school of Symbolism, and wrote the Symbolist Manifesto. In his lifestyle and dress, he was a noted exponent of dandyism, and his verse was marked by the highly embellished mannerisms of the Symbolist school. His later work is marked by a return to classicism and the style of the Parnassians.
His most important publications were:
Poems of Jean Moréas (in French): http://poesie.webnet.fr/auteurs/moreas.html