The study of palynofacies along a core drilled on the coastal plain of Cabo Frio, State of Rio de Janeiro, was carried out in order to contribute to the knowledge of the paleoenvironmental evolution of the Pero Beach region. The ages obtained from 14C datings allowed to verify that the studied core records the past 6761±130 yrs cal BP. Thirty samples were prepared by standard methodology for palynofacies. About three hundred particles of the particulate organic material was classified and recorded for each sample. Statistical methods were employed for the associations of particulate organic matter (R-mode cluster analysis) and levels (samples; Q-mode cluster analysis) analyzed along the core. Furthermore, the ratio Phytoclast-Total Organic Carbon (Phy-TOC) was used to verify the proximity of the source area. The three major groups of particulate organic matter found along the studied core are Phytoclasts, Amorphous Organic Matter (AOM) and Palynomorphs. The samples showed in general, a predominance of phytoclasts (73.2%), followed by AOM (18.6%) and Palynomorphs (8.2%). Supported by statistical analysis, it was possible to deduce that the study area evolved since the middle Holocene from a marine environment to a paleolagoon.