The Thracian Plain in the SE Balkans was one of the main corridors through which Neolithic agriculture spread into continental Europe. Previous studies have invoked rapid sea-level and climatic changes to explain the timing of agricultural expansion. We present a new record of vegetation, fire and lacustrine sedimentation from Bulgarian Thrace to examine environmental change in this region since the Last Glacial Maximum. Our record indicates the persistence of cold steppe vegetation from ∼37,500 to 17,900 cal. a BP, semidesert vegetation from ∼17,900 to 10,300 cal. a BP, forest-steppe vegetation from ∼10,300 to 8900 cal. a BP, and mixed oak woods from ∼8900 to 4000 cal. a BP, followed by widespread deforestation, burning and grazing. Early-Holocene forest expansion in Bulgarian Thrace closely followed changes in the Black Sea's regional moisture balance and appears to have been influenced by solar-forced changes in seasonality. We suggest that climatic aridity and/or enhanced seasonality - lasting until at least ∼8900 cal. a BP - could have delayed the spread of early agriculture from the Aegean coast into the continental lowlands of the Balkans and thence into the rest of Europe.