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The main goal of this paper is to contribute to the understanding of the geological and geomorphological evolution of Papagaios Island, located off Cabo Frio, SE Brazil. This sector of the Brazilian coastline lies in the transition between Campos and Santos basins, two prolific oil-bearing areas. Contrarily to other nearby coastal islands trending along a NE-SW axis, Papagaios Island is structurally oriented in the NW-SE direction. Lithologically, it is predominantly constituted by high grade gneisses from the Buzios Succession, a sequence of Neoproterozoic supracrustal rocks (mainly paragneisses, amphibolites, biotite gneisses, calcsilicates and quartzites). These rocks were deformed and metamorphosed during the Cambrian period; they are intercalated parallel to the main metamorphic foliation (S-1/2), which is folded, forming recumbent mesoscopic structures with a sub-horizontal axis NW-SE. The main brittle structures are characterized by normal dextral faults and subvertical fractures with NE-SW strike. At least thirty-six, 2-15 In thick dolerites, related to Mesozoic evolution of the Brazilian margin, have been mapped. Papagaios Island presents a crenulated, steep coastline along which several features such as indentations, crevices, gorges and marine caves are observed; only one sandy beach and two zones of pebble accumulation were found. The lithotypes show distinct degrees of resistance, resulting in highly variable erosion rates. The ductile and brittle structures facilitate the operation of the weathering processes, contributing to decrease rock resistance. Wave exposure combined to the structural orientation and distinct lithotypes seem to control the geomorphological evolution Of this island; semi-arid climate conditions do not favor subaerial weathering processes.