In this paper we present the first palynomorph and mollusc assemblages from the sediments in three different sections. From east to west, these are the Şevketiye (northern Biga Peninsula), the Tayfur (Gelibolu Peninsula) and the Kuzu harbour (Gökçeada) (parts of the Danişmen Formation) sections in the south and south-western side of the Thrace Basin (north-west Turkey), with the aim of obtaining information about the composition and structure of vegetation and climate during the Oligocene. The stratigraphic interval extends from late Rupelian to Chattian. The Danişmen Formation in the Şevketiye section yielded a palynomorph association with abundant coastal palms (Arecaceae; Lepidocaryoidae), and mangrove pollen (Pelliciera). A similar assemblage from the Kuzu harbour section was also obtained, with minor contributions of mangrove elements Nypa and Acrostichum aureum, Arecaceae type palm, undifferentiated dinoflagellate cysts and microforaminiferal linings. These palynomorph assemblages, combined with the mollusc data, indicate that low-lying coastal environments prevailed. In contrast, the palynomorphs from the Tayfur section represent a non-marine environment lacking mangrove elements, palm trees, dinoflagellate cysts and microforaminiferal linings. The diversity of angiosperm taxa in the Tayfur palynoflora, which form the bulk of the assemblage, indicates terrestrial vegetation. Quantitative palaeoclimate analyses are based on the Coexistence Approach method, and yield over 22 °C at the coast as indicated by mangrove elements and palms in the Şevketiye and Kuzu harbour palynofloras. For the Tayfur palynoflora, mean annual temperature ranged between 16.5 and 21.3 °C. This indicates a climate cooling, corresponding to the transition from Rupelian to Chattian, and resulted in the pollen changes from mangrove bearing coastal deposits to more inland vegetation. © Tübi̇tak.