Abstract: The northern Indian Ocean is one of the most significant marine sedimentary systems globally, characterized by highly complex depositional environments and processes. The study of sediment composition and provenance in this region is crucial for enhancing the understanding of "source-to-sink" processes in continental shelf marginal seas. In this study, a total of 19 surface sediment samples were collected from the key areas of the northern Indian Ocean—the Arabian Sea and the Ninety East Ridge in the southern Bay of Bengal during the DY72 Ocean survey voyage, the grain size, mineral composition, and elemental geochemistry were analyzed to comparatively investigate the composition, distribution, and controlling factors of sediments in these two regions, and to explore the sources of the sediments and the differences between the regions. The results showed that the sediments in the study area were mainly clayey silt, and the sediments in the basin area were finer and better sorted than those in the ridge area. The mineralogical and elemental geochemical characteristics indicated that the sediments in the study area were mainly calcareous ooze, but there were also obvious mixed features of terrigenous components. However, the proportion of terrigenous components in the Arabian Sea sediments was higher, while the sediment in the Ninety East Ridge showed a typical biogenic carbonate-dominated pattern. The composition and distribution of sediments are mainly controlled by the sediment sources restricted by topography. Rare earth element (REE) provenance discrimination revealed that the terrigenous components in Arabian Sea sediments were mainly influenced by materials from northeastern Africa and western India, while the Ninety East Ridge was predominantly affected by inputs from the Ganges-Brahmaputra River system.