This dataset contains planktonic foraminifera assemblage groups defined by cluster analysis, alongside sea surface temperature (SST) reconstructions generated with the Modern Analogue Technique (MAT). The record spans 0.5 to 1.3 Ma, covering intervals before, during, and after the Middle Pleistocene Transition (MPT). Sediments were recovered by drilling during IODP Expedition 383 at Site U1539, located in the South Pacific sector of the Southern Ocean. Samples were washed through a 63 µm sieve, dried at approximately 50°C for 24 hours, and subsequently sieved through a 250 µm mesh. Species-level identification was performed using a stereomicroscope. Counts of each species were converted into relative abundances (%), which were then used as input for cluster analysis performed in PAST Software (version 4.14) applying the unweighted pair group method with arithmetic mean (UPGMA) algorithm and the Bray–Curtis similarity index. The dataset includes the sample code, depth in meters CSF-A (core depth below seafloor, method A), interpolated age in million years (Ma), MAT-derived SST estimates (°C) with corresponding weighted standard deviations, and the cluster group assigned to each sample following the classification proposed by de Castro et al. (2025; doi:10.1016/j.marmicro.2025.102501). These data were used as proxies to reconstruct and characterize paleoceanographic changes in the central South Pacific between 0.5 and 1.3 Ma, encompassing the MPT. MAT analysis, which was performed following the previous description by Hutson (1980; doi:10.1126/science.207.4426.64) and Kucera et al. (2005; doi:10.1016/j.quascirev.2004.07.014).