He moved to Austria in 1809, where he became a diplomat and journalist in service of Klemens von Metternich, the Foreign Minister of the Austrian Empire.

The first to notice what became known as Grimm's law, Schlegel was a pioneer in Indo-European studies, comparative linguistics, and morphological typology, publishing in 1819 the first theory linking the Indo-Iranian and German languages under the Aryan group.

In Jena he and his brother founded the journal Athenaeum, contributing fragments, aphorisms, and essays in which the principles of the Romantic school are most definitely stated.

There he lived with Friedrich Schleiermacher and met Henriette Herz, Rahel Varnhagen, and his future wife, Dorothea Veit, a daughter of Moses Mendelssohn.

[13] Lucinde, which extolled the union of sensual and spiritual love as an allegory of the divine cosmic Eros, contributed to the failure of his academic career in Jena[12] where he completed his studies in 1801 and lectured as a Privatdozent on transcendental philosophy.

In June 1802 he arrived in Paris, where he lived in the house formerly owned by Baron d'Holbach and joined a circle including Heinrich Christoph Kolbe.

He lectured on philosophy in private courses for Sulpiz Boisserée, and under the tutelage of Antoine-Léonard de Chézy and linguist Alexander Hamilton he continued to study Sanskrit and the Persian language.

In April 1804 he married Dorothea Veit in the Swedish embassy in Paris, after she had undergone the requisite conversion from Judaism to Protestantism.

He went to Vienna and in 1809 was appointed imperial court secretary at the military headquarters, editing the army newspaper and issuing fiery proclamations against Napoleon.

In collaboration with Josef von Pilat, editor of the Österreichischer Beobachter, and with the help of Adam Müller and Friedrich Schlegel, Metternich and Gentz projected a vision of Austria as the spiritual leader of a new Germany, drawing her strength and inspiration from a romanticised view of a medieval Catholic past.

In 1820 he started a conservative Catholic magazine, Concordia (1820–1823), but was criticized by Metternich and by his brother August Wilhelm, then professor of Indology in Bonn and busy publishing the Bhagavad Gita.

Friedrich Schlegel's wife, Dorothea von Schlegel, authored an unfinished romance, Florentin (1802), a Sammlung romantischer Dichtungen des Mittelalters (Collection of Romantic Poems of the Middle Ages) (2 volumes, 1804), a version of Lother und Maller (1805), and a translation of Madame de Staël's Corinne (1807–1808) — all of which were issued under her husband's name.