The mollusk collection began in 1860 with the purchase of the land and freshwater snails of J.G. Anthony, who later joined the staff of the MCZ in 1865 as its first curator. Until his death in 1877, he carried on a very active exchange with museums and private collectors all over the world including England, France, Germany, Spain and Australia and tried to acquire authentic specimens of every species he could. In 1876 he began a special effort to exchange with people describing new species in order to obtain type-specimens and as a result, the collection is rich in type material received from workers of the day. The outstanding purchase during Anthony's curatorship was that of the William Harper Pease collection primarily of Pacific mollusks.

Following Anthony's death, the collection was cared for by curators interested in mainly other fields. Nonetheless, it continued to grow as a result of the voyages of Alexander Agassiz. Though never officially appointed as the Curator of Mollusks, William F. Clapp served as curator from 1911-1923. The MCZ activities were reduced by the war and financial difficulties at this time, so there were no major voyages or expeditions, but several large collections came to the museum.

William J. Clench was appointed as Curator of Mollusks in 1926 and published many scientific papers until his retirement in 1966. He worked toward having a well-balanced world wide research collection, through exchanges, collecting trips and acquisition of collections from small private museums which could no longer afford to care for them. Acquired during Clench's curatorship, the S. Putzey collection was an important addition because Putzey was exchanging and building his collection during the period between Anthony and Clench when there was less activity in the department. Kenneth J. Boss assumed curatorship in 1966 and continued in the traditions of past curators.

From 1941-1974, Johnsonia (Monographs on the Western Atlantic), brought marine material into the museum from people who were interested in this publication.   And then beginning in 1945, Occasional Papers on Mollusks provided a forum for long, well-illustrated research papers and had become an important resource in the study of malacological history due to its extensive biographies, bibliographies, and catalogues. Special Occasional Papers [on Mollusks] published larger monographs and bibliographic works. 

Because of the interests of its founder, Louis Agassiz, the MCZ, including the mollusk collection, has been strong in the marine organisms from its inception. Marine material has come to the MCZ from a number of sources including voyages, expeditions, gifts and purchases. In addition, entire collections of many small museums that could not support a mollusk collection have been acquired by the MCZ. Agassiz also obtained valuable material, much of it marine mollusks, from the Atlantic, Gulf of Mexico and the Pacific coast of Mexico.

The collection of shipworms and piddocks (Teredinidae and Pholadidae) far exceeds any other collections of these families due to the research of Ruth D. Turner. The scaphopods, deep sea bivalve and gastropod collections are generally rich as a result of the Department's close association with Woods Hole Oceanographic Institution and the many cruises in which various members of the staff have participated. All groups monographed in Johnsonia are considerable in size and well curated. The chiton collection, which was subject of graduate student's research in the 1960's, is also extensive.

The holdings of land mollusks in the MCZ reflects the great diversity of the two major lineages of gastropods which have invaded the terrestrial habitat: the lunged snails, or pulmonates, and the air-breathing prosobranchs. The Department maintains a broad spectrum of all prosobranch and pulmonate land forms but is particularly rich in the areas of: North America, Achatinellidae of the Hawaiian Islands, European and Asian clasusiliids, West Indian Cerionidae, African Achatinidae, South American Strophocheilidae and the arboreal bulimuloid Liguus of the Florida Keys. Other families including the Helicinidae, Cyclophoridae, Pomatiasidae and Truncatellidae are particularly well represented.

The MCZ has one of the larger assemblages of freshwater mollusks in the country, representing extensive geographic areas. Beginning with the acquisition of J.G. Anthony's collection of freshwater mollusks in 1863, the holdings continued to grow. From 1926-1961, W.J. Clench made numerous trips to the southern United States to collect freshwater mollusks. Additionally, between 1914-1944, all of the freshwater mollusks from the museum of Boston Society of Natural History, as well as those of the Grand Rapids (Michigan) Public Museum and the extensive duplicate collection of Bryant Walker from the Museum of Zoology at the University of Michigan were obtained. In 1930, Dr. J. Bequaert presented the MCZ with an important series of freshwater shells principally from Africa and southeast Asia. A remarkable number of Unionidae and Corbiculidae types were purchased 1946 from the Musee Heude in Shanghai. Finally, the MCZ has the Prime collection of Corbiculidae and Sphaeridae as well as the Roper collection. Among the gastropods, the Pleuroceridae, Lymnaeidae and Planorbidae are well represented.