This dataset contains quantitative calcareous nannofossil assemblage data from ODP Site 121-752A spanning the Middle to Late Miocene. Specifically the interval comprehended between 7.34 - 16.06 Ma. ODP Site 752 drilling procedures were carried out by the D/V JOIDES Resolution as part of ODP Leg 121. Samples presented in this entry were obtained using APC coring (see Shipboard Scientific Party, 1988; doi:10.2973/odp.proc.ir.121.106.1989). Sampling was conducted in the Kochi Core Center (KCC).The quantitative nannofossil assemblage data was generated at the University of Graz (Austria) on a ZEIS Axio Lab.A1 and a field of view of 220 µm (22/10X objective; 100X magnification). The assemblage data includes also the counts of reworked material. The dataset also includes additional information such as sample volume (mL), dilution (mL) and weight (g), allowing for calculation of total abundances in number of liths per gram of sediment, following the methodology of Bordiga et al. (2015; doi:10.1016/j.revmic.2015.05.002). the age provided in this dataset derive from the astronomically tunned age-depth model from Lyu et al., (2023; doi:10.1029/2023PA004761).The present data was generated to study the past climate evolution of the surface water conditions of the southern Indian Ocean during the Middle to Late Miocene. Specific details regarding the hypotheses and major outcomes of the study can be found in the associated publication.