Shells of marine molluscs exploited by prehistoric humans constitute archives of palaeoecological and palaeoclimatic data, as well as of human behaviour in coastal settings. Here we present our investigations on the mollusc assemblage from Ksâr 'Akil (Lebanon), a key site in southwestern Asia occupied during the Middle and Upper Palaeolithic. The site plays an important role in understanding modern human dispersals into Eurasia. Taxa from intertidal rocky shore, subtidal soft bottom, and rocky littoral habitats dominate the marine component of the invertebrate assemblage. Terrestrial snails indicate wooded and open half shaded habitats in the vicinity of the site. Species composition suggests that these habitats were present throughout the Upper Palaeolithic. Humans transported marine molluscs to the rockshelter as ‘food packages’ for dietary purposes (e.g., Patella caerulea, Patella rustica, Phorcus turbinatus) and shells of other taxa to be used as tools (e.g., Glycymeris sp.) or possibly for ornamental purposes (e.g., Nassarius gibbosulus and Columbella rustica). In the Initial Upper Palaeolithic, collection focussed on empty shells as raw material for utilitarian purposes. In the subsequent Early Upper Palaeolithic and later periods, mollusc gathering was performed in an increasing number of habitats and shifted towards collection for human consumption, which was the main reason for the introduction of shells to the site during the Epipalaeolithic. Concurrent size shifts of live collected as well as beached specimens suggests that size changes were linked to environmental change rather than to potential overexploitation of dietary taxa by humans.