This study addresses the paleogeographic coastal evolution of the coastal plain in the environs of Iskele, Turkey. Eight sediment cores were collected along a north–south and east–west transect and analyzed to determine whether the coastal environment had changed in the recent past. The results illustrate that the coastal environment consisted of a transgressive systems tract, ending approximately 6000 BP and represented by marine transgression, flooding of incised river channels, and marsh development, followed by a high stand systems tract. Five major environmental facies were identified: terrestrial, wetland, lagoon, foreshore, and upper shoreface. The high stand systems tract was characterized by the development of a beach-barrier consecutive series of longshore transport-derived sandbars. These sandbars contributed to the creation and eventual isolation and terrestrial infilling of nearshore lagoons and wetlands. Sea-level indicators indicate rapid sea-level rise reaching a peak approximately 6000 YBP, followed by deceleration of sea-level rise and resulting shoreline progradation. The construction of a causeway connecting Karantina Island to the mainland approximately 2400 years ago has accelerated the process of progradation east of the causeway by decreasing the wave energy. Sediment that would have previously been transported further east is now deposited in the zone immediately east of the causeway.