This article addresses the controversial question of Theodor W. Adorno’s debt to right-wing Zivilisationskritik by a close reading of his essay “Spengler after the Decline” (1950). The article shows that despite Adorno’s harsh polemics against Oswald Spengler’s Decline of the West (1918, 1922), he sought to make Spengler’s analysis of Weimar Germany’s undemocratic tendencies—“Caesarism”—serve progressive ends. However, Adorno’s essay was not just an effort at “coming to terms with the past” in Adenauerian West Germany. Reading the essay’s original 1941 version together with Adorno’s correspondence with Max Horkheimer sheds light on Spengler as an overlooked key (next to Max Weber, Sigmund Freud, and Walter Benjamin) to their Dialectic of Enlightenment, written in 1941–44. Adorno’s daring effort to appropriate Spengler’s analysis of Caesarism makes Adorno’s critical theory an asset in understanding today’s authoritarian populism.