The paper is devoted to an overview of Cassirer’s work both as historian of philosophy and historian of science. Indeed, the “intelletcual cooperation” between history of philosophy and history of science represents an essential feature of Cassirer’s style of philosophizing: while the roots of a wide exploration stretching from Renaissance thought to modern physics go back to the Neo-Kantianism of the Marburg School, the results of a similar cross-fertilization of research fields have deeply contributed to shaping new standards of inquiry. Cassirer’s relationship with the Warburg milieu in Hamburg and late in his life with the American intellectual scenario (for instance, with the “Journal of History of Ideas”) are surely worthy of closer investigation. Distinguished scholars such as Meyerson, Brunschvicg, Burtt, Koyré, Metzger, Lovejoy, Kristeller, have disussed, appreciated, critizised Cassirer’s still today fascinating studies devoted to Pico della Mirandola, Galileo, Newton, Leibniz, to mention but a few. To explore some of these aspects focusing both on affinities and differences within a cosmpolitian intellectual community can provide a better understanding of philosophy and history of science in the first half of 20th century. Cassirer’s legacy requires, therefore, a new assessment.