The area of this study is the Lagoa Grande das Queimadas archaeological site, located in the southwest of the state of Piaui, in the semi-arid region of Northeast Brazil, a region that is globally recognized for its archaeological and paleontological heritage. The use of biogenic silica (especially phytoliths) as proxies for paleoenvironmental reconstruction aimed to evaluate the paleoenvironment of ancient human occupations. The phytolith assemblages recovered from the sediment record of the Lagoa Grande das Queimadas archaeological site are predominantly composed of Poaceae morphotypes, mainlyBLOCKY, BULLIFORM FLABELLATE, ACUTE BULBOSUS, and ELONGATE, with a reduced presence of woody dicotyledons (SPHEROID ORNATE). Arecaceae phytoliths (SPHEROID ECHINATE) are also observed throughout the profile, increasing from the oldest to the most recent sample, along with fragments of sponge megascleres and microcharcoals. The results revealed that this region experienced climatic variations during the Greenlandian to Meghalayan, as demonstrated by the phytolith and aquatic bioindicator (sponge spicules and diatom frustules) records. The analyses indicate that between 12,908-12,478 and 4420-4233 cal yrs BP, the temperature and humidity increased progressively, followed by a transition from a more humid climate than at present to drier conditions starting from 4420-4233 cal yrs BP. The qualitative and quantitative results of the phytolith analyses, associated with other proxies studied at this site, contributed to constructing information about the archaeological site and its insertion into the landscape, in addition to understanding the mobility and subsistence models of past human groups during the Holocene in the interior regions of Northeast Brazil.