Later in his life, before and during World War I, he became an ardent nationalist and anti-socialist politician, with close ties to the Fascist movement. He was Minister of Finance in the Carnaro government of Gabriele D'Annunzio at Fiume, which lasted for fifteen months between 1919 and 1920. Shortly before his death, he was appointed to the Italian Senate by Benito Mussolini.

Major works of Maffeo Pantaleoni

• Teoria Della Traslazione dei Tributi, 1882.
• "Contributions to the Theory of the Distribution of Public Expenditure", 1883.
• Dall 'ammontare probabile della Richezza Privata in Italia, 1884.
• Pure Economics, 1889.
• "A proposito di Luigi Cossa e della sua "Histoire des Doctrines économiques", 1898, GdE
• "Dei criteri che devono informare la storia delle dottrine economiche", 1898, GdE
• "An attempt to analyze the concepts of "Strong" and "Weak" in their economic connexion", 1898, EJ
• "Una visione cinematografica del progresso della scienza economica, 1870-1907", 1907, GdE
• Note in Margine della Guerra, 1917.
• Politica, 1918.
• Erotemi di Economica, 1925.