A detailed Holocene sedimentological and geomorphological history of the sedimentary infill of Lake Conjola, a barrier estuary on the southeast coast of Australia, is presented. Results show that a remnant Last Interglacial barrier system is preserved in the mouth of a narrow incised valley. During the early stage of Holocene sedimentary infill, a laterally extensive transgressive sand facies was deposited as rising post-glacial sea-level breached remnants of the Last Interglacial barrier ca. 7500 cal BP. From 7500 to 4000 cal BP sediment continued to accumulate within the mouth of the incised valley, forming an extensive flood-tide delta within the drowned river estuary. Marine influences were restricted by further sediment accumulation at the mouth of the estuary, leading to the development of mid-Holocene barrier and back-barrier depositional environments. This research adds detail to stratigraphic models of the sedimentary infill and geomorphological evolution of barrier estuaries formed in narrow incised valley systems on the southeast coast of Australia, and provides a global model for estuarine deposition in regions that have been tectonically stable over the late Quaternary.