Fifty-two species of hermit crabs of the families Coenobitidae, Diogenidae and Paguridae were collected in the Arafura Sea and in Maluku (Moluccas), Indonesia. Five of these species were previously unrecorded from the Arafura Sea and Torres Strait. At the Banda Islands. where the major part of the collecting was done, 34 out of 37 species are reported for the first time. The collection included 18 new records for Seram and 14 for Saparua. Four new species are described from maluku. Live colour notes and information on natural history are presented for most of the species in the collection, and associations are noted with anemones, rhizocephalans, cirolanid and parasitic isopods, copepods, a shrimp and a polychaete.