In this study of asellote Isopoda from the Indian Ocean, 29 species in 11 genera and seven families are recorded. Twenty-one species are described as new: family Gnathostenetroididae, Maresiella aldabrana; family Janiridae, Carpias mossambica; family Joeropsidae, Joeropsis algensis, J. arpedes, J. dimorpha, J. hamatilis, J. lentigo, J. pentagona, J. pleurion; family Pleurocopidae, Pleurocope wilsoni; family Pseudojaniridae, Pseudojanira meganesus; family Santiidae, Santia spicata, S. urospinosa; family Stenetriidae, Hansenium aldabrae, H. expansa, H. remocarpus; Mizothenar serratum, Stenetrium assumentum, S. quinquedens, S. zanzibarica, Stenobermuda brucei. The erst record of the family Pleurocopidae (Pleurocope wilsoni) and the genus Mizothenar (family Stenetriidae) from the Indian Ocean are included. Diagnoses of the genera and species are provided, and keys to the Indian Ocean species of most of the genera. The material comes primarily from Aldabra Atoll, the granitic Seychelles islands, Zanzibar Island, the Comoro Islands, and Phuket in Thailand. A few samples are from material of the International Indian Ocean Expedition carried out in the mid-1960s.