The Library of modern foreign languages and literatures hosts a collection of about 200,000 volumes. It extensively documents and provides high-level specialized content in the fields of English, German, French, Slavic, Hungarian, and, to a lesser extent, Flemish and Nordic languages and literatures. Over the years, it has acquired valuable library collections (Malvezzi, Paul Valery, Mac Pherson, Bertea, and others) and houses around a hundred rare books, including some valuable 17th-century volumes. 

One of its strengths is the Slavic section, with around 80,000 volumes of Russian, Polish, Czech, Slovak, Serbian, Croatian, Slovenian, Ukrainian, Macedonian, and Belarusian languages and literatures. Thanks to the acquisition of several collections over the years (the private libraries of Ripellino, Nicolai, Martini, Lo Gatto, Costantini, Zahorski), it is held to be the richest and most valuable Slavic collection in Western Europe.