Snails and mussels (molluscs) represent one of the focal points of the collections at the Natural History Museum Basel. The collection integrates some of the oldest objects in the museum, and comprises both dry material (shells) as well as alcohol-preserved and on microscope slides. The collection includes around 130,000 specimens from 12,000 species.

The scientifically significant mollusc collection also includes material from a series of authors dating from the 19th and the early 20th centuries. It also contains the extensive collection brought back by Fritz and Paul Sarasin from their expeditions.

The Western Pacific region, especially New Caledonia, New Guinea and other Melanesian islands, is well-represented, as are sea slugs (Nudibranchia), thanks to the collection from Hans-Ruedi Haefelfinger. Unlike land snails, these aquatic species are always preserved in alcohol.

Lothar Forcart was the last mollusc researcher (malacologist) at the Natural History Museum Basel. Thanks to his contacts and activities, the collection was used extensively until his death in 1990 and constantly expanded.

The collection has been increased in more recent times by the reference collections for the Biodiversity Monitoring Project of Switzerland, as well as those from Switzerland's Red List of molluscs.