With a major emphasis for the Quaternary period, paleoceanographic studies of the Indian Ocean were reviewed. The climatic system of tropical Indian Ocean, characterized by the SW (summer) and NE (winter) monsoons, is unique, and the Quaternary histories of the marine biota as well as the sedimentation flux are different from those of other world oceans. The strong upwelling generated by the SW monsoon off the coast of Arabian Peninsula has been a subject of intensive studies, and the history of SW monsoon is now regarded as: initiated at ca. 10 Ma, became strongest at ca. 5 Ma, followed by gradual weakening through the early Quaternary, and finally, entered to the late Quaternary oscillation phase corresponding to the glacial-interglacial cycles. It is now evident that the monsoon intensified during the interglacial periods and weakened during the glacials. There are contradictory views for the timing of aridity on the African continents and also for the transporting mechanism of the terrigenous material at the off coast of Oman. Although the majority of micropaleontological studies for the Quaternary history of the Indian Ocean have been based upon the planktonic and benthic foraminifera, calcareous nannofossils are emerging as a useful tool. Some of the preliminary results from the recent studies of calcareous nannofossils at the north-central and south-eastern Indian Ocean are also briefly reviewed.