This dataset presents palynological data obtained from the Monte San Nicola type section (Mediterranean Basin, Italy, Sicily), which hosts the Global boundary Stratotype Section and Point (GSSP) for the base of the Quaternary. The data were collected within the framework of the informal GELSTRAT working group of the Subcommission on Quaternary Stratigraphy (SQS, ICS). The pollen record spans a key interval in Earth's history corresponding to the intensification of Northern Hemisphere glaciation (ca. 2.7-2.5 Ma) in the section where the Global boundary Stratotype Section and Point (GSSP) for the base of the Quaternary is defined. Pollen grains were identified and counted following standard palynological procedures. The dataset includes percentages for the identified taxa and ecological informal groups. These data contribute to the reconstruction of local and regional vegetation patterns and provide insights into environmental and climatic changes during the Plio-Pleistocene transition (MIS G4-MIS 99). The dataset supports paleoclimatic, paleoenvironmental, and stratigraphic studies focused on the onset of Northern Hemisphere glaciation.