With some 130,000 items, the Bibliothèque’s poster collection is one of the most significant in Switzerland. The collection, which is associated with the Département du Dépôt legal (the Legal Deposit Department), features above all Genevan posters (broadly speaking), along with a selection of Swiss posters. It boasts 19th-century typographic posters (some of which are embellished with engravings), as well as comic book posters, posters related to politics, culture, and advertising, and unauthorized or underground posters from the 1970s. The collection even has a few banned posters that were never pasted up on the city walls. Founded in Geneva in 1900, the Société générale d’affichage (SGA) has entrusted the Bibliothèque with its collection of historical posters, some 8,000 pieces, an admirable complement to the library’s existing collections. The collection shows life in Geneva from a perspective that differs from printed matter (both books and periodicals) while revealing a little-known visual facet of Geneva.

Since 2001, the posters have been accessible online at the Catalogue Collectif suisse des affiches (the Swiss Poster Collection) and Europeana. Each notice includes a thumbnail.

The oldest posters are conserved in the Rare books department.

The Bibliothèque has been collecting posters since 1851. Collecting is a more apt term than conserving since the works were not catalogued in those early days and the posters were not accessible to the public. This corpus continued to grow until 1907 (year that the legal deposit law was repealed). Other posters were added to the collection. In 1969, new legislation concerning the legal deposit was enacted, a law to which posters were also subject. And since the 1980s, the Bibliothèque has enjoyed the support and assistance of the Société générale d’affichage (SGA) in enriching its collections.