The article presents a painted portrait, the only one known to date, of Cardinal Francesco Maria Sforza Pallavicino (1607-1667), friend and collaborator of Pope Alexander VII Chigi. The work is compared with other portraits of the cardinal, propagated by engravings that celebrated his appointment as cardinal or that preceded the text in printed editions of his literary works, and the famous Bernini drawing now at Yale University. On stylistic grounds, the attribution of the canvas to Giovanni Maria Morandi, one of the most active portrait painters at the court of Alexander VII, is proposed. Tracing the history of the painting's ownership up to its current location in the British Embassy to the Holy See, it is suggested that the commissioner may be Ernest of Hesse-Rheinfels (1623-1693), who converted to Catholicism precisely through the intercession of Pallavicino, with whom he had an exchange of letters.