Bats play key ecological roles on the islands of Aruba, Bonaire and Curaçao (ABC islands), Caribbean Netherlands; however, most bat species on these islands are either threatened or their conservation status is unknown. We investigated the use of roosts by cave-dwelling bats in this insular system to propose conservation measures aimed at their protection. We conducted bi-monthly species inventories of cave-dwelling bats in 13 of the best-known caves and mines used as day and maternity roosts on the ABC islands. Bats were captured with mist nets and a harp trap (only one cave) placed either inside or at the entrance of the roosts during the first hours (3 to 5 hrs) after sunset. For Aruba and Curaçao, bat monitoring comprised two years of sampling. In the case of Bonaire, depending on the cave, bat monitoring involved one, two or four years of sampling. We identified six species of cave-dwelling bats associated with these roosts, Mormoops megalophylla, Pteronotus davyi, Natalus tumidirostris, Myotis nesopolus, Glossophaga longirostris and Leptonycteris curasoae. All the examined caves and mines were occupied year-round. The two abandoned mines were inhabited exclusively by the nectar-feeding G. longirostris and L. curasoae, whereas caves containing hot chambers were occupied by up to five species of bats, including insect-feeding M. megalophylla, P. davyi, M. nesopolus and N. tumidirostris, and migratory L. curasoae. Nursery roosts occupied by insect-feeding bats were Quadirikiri on Aruba; Orizjan, Pos di watapana and Pos di Antoin on Bonaire; and Raton and Noordkant on Curaçao. Nectar-feeding bats used all the caves and mines examined as day roosts, nursery roosts or both. All the cave-dwelling bats studied had a single annual reproductive period. In the case of insectivorous bats, pregnancy and lactation occurred mainly between July and December, overlapping with the rainy season. For nectar-feeding bats, pregnancy and lactation took place between March and September, overlapping with the flowering and fruiting seasons of chiropterophilous cacti. Most of the examined bat roosts require protection due to one or more of the following conditions: (1) the presence of multiple species dependent on hot chambers, (2) their use as nursery roosts, and (3) the presence of large colonies of L. curasoae.