In 1880, after serving as Viennese correspondent for a Budapest newspaper and traveling extensively in Europe, Nordau settled permanently in Paris, where he established a medical practice. A prolific writer of travel books, plays, poems, and essays, he achieved his greatest success in 1883 with Die conventionellen Lügen der Kulturmenschheit (The Conventional Lies of Our Civilization), a vitriolic attack on the inadequacy of 19th-century institutions to meet human needs; he took a particularly harsh look at organized religion. Banned in Russia and Austria, the book nevertheless was translated into numerous languages and went into some 73 editions.

After he met the charismatic Jewish nationalist Theodor Herzl (Herzl, Theodor) in Paris in 1892, Nordau became deeply interested in Zionism and served as vice president of the Zionist congresses under Herzl, delivering a number of brilliant addresses on the condition of world Jewry. Following Herzl's death in 1904, Nordau broke with the “practical Zionists” (younger men advocating colonization of Palestine without guarantees of political sovereignty), who gained control of the Zionist congresses; Nordau refused to participate in these meetings after 1911.