Here we present a stalagmite-based annual-resolved hydroclimate record, with a mean sampling resolution of 1.1 yr, spanning 154–529 CE from Börtlüce Cave, western Türkiye, encompassing the latter part of the Roman Warm Period (RWP) and the transition into the early Dark Ages Cold Period. During the late RWP, elevated Mediterranean Sea surface temperature (SST) likely enhanced cyclone activity and moisture transport, promoting persistently humid conditions. The subsequent transition from 290 to 430 CE was characterized by pronounced multi-decadal hydroclimatic variability, likely reflecting the combined influences of Mediterranean SSTs, large-scale atmospheric circulation associated with the North Atlantic Oscillation, and solar variability. The reconstructed humid conditions broadly coincide with the period of prosperity and territorial expansion of the Roman Empire, whereas the following increase in hydroclimatic instability may have amplified the environmental stresses during the decline of the Western Roman Empire. Our findings highlight the complex interplay among Mediterranean SST, atmospheric circulation, volcanic eruption, and solar forcings in shaping the eastern Mediterranean hydroclimate through the early Common Era.