The relationship between the Qajar rulers of Iran and the Vatican constitutes a little-known thread of diplomatic and cultural interaction, sustained by Papal correspondence, gift-giving, Apostolic Delegates and mutual respect, which spanned the nineteenth and early twentieth centuries. The well-being of Iran’s small Catholic population was a desideratum of Popes, from Pius VII to Benedict XV, but firmans issued by Qajar Shahs offered guarantees which were often ignored on the ground. Iran’s Catholics became unwitting pawns in the decades-long rivalry between American Presbyterians and French Lazarists, and nascent Iranian diplomacy in Europe took great care in matters concerning the Vatican.