Abstract The arrival of large numbers of Yemeni manuscripts in European libraries towards the end of the nineteenth century and in the early twentieth century was a sensation that was enthusiastically received by the scholarly world. One of the principal reasons for this enthusiastic reception was the upsurge of South Arabian studies in Europe since the first half of the nineteenth century, together with the hope that the new material would fill some of the gaps in the literary sources on the history and geography of southern Arabia, especially during the pre-Islamic period. The most significant such lacuna was the missing volumes 1 through 7 and 9 of al-Hamdānī’s Iklīl. The two most important collections of Yemeni manuscripts that arrived in Europe in the late nineteenth and early twentieth centuries had been gathered by Eduard Glaser and Giuseppe Caprotti, respectively, and their collections were sold to Berlin, London, and Vienna (Glaser) and to Munich, Milan, and the Vatican (Caprotti). The collections included some new material on South Arabian history (including volumes 1, 2, and 6 of the Iklīl), but they also opened up entirely new vistas and laid the foundation for the new discipline of Zaydi studies. Unlike South Arabian studies, the study of Zaydism had a slow start, with initially only a few scholars being interested in this entirely new field. Moreover, the scholarly exploration of the respective subcollections depended on the availability of catalogues. The early history of the Caprotti collection is intimately linked to Eugenio Griffini. Caprotti had dispatched nearly his entire manuscript collection of some 1,600 codices to Griffini, who kept it in his apartment in Milan until 1909, when the collection was donated to the Ambrosiana Library. Griffini was also the first and, for a long time, the only scholar to study the collection and prepare studies as well as catalogues of it. The process of his engagement with the material can be reconstructed on the basis of the Griffini archive, the whereabouts of which were for decades uncertain. This study outlines the discovery of the Griffini archive in the Biblioteca Comunale Centrale Palazzo Sormani in Milan and provides an initial overview of its contents, including Griffini’s epistolary exchanges with some ninety-nine correspondents, his descriptions of some of the Ethiopic manuscripts of the Ambrosiana, and, most importantly, his schedario, containing his extensive notes on all manuscripts of series A of the Caprotti collection. The large corpus of so far unexplored material promises to provide new insights into the network of Islamicists and Arabists at the turn of the twentieth century and the nascent phase of Zaydi studies in Europe.