Abstract Grain-size analysis of the sediments in borehole M0079A, located in the Corinth Rift, was used to explore hydrodynamic conditions and provenance in the Late Pleistocene Corinth Rift. Grain-size populations that were sensitive to the sedimentary environments were characterized by frequency distribution, particle size–standard deviation and probability cumulative curves. Our results indicate the grain-size population component in the range 0.15–0.25 µm may be used as a sensitive proxy for hyperpycnal flows, which have commonly been triggered by river floods from the southern margin of the rift since c. 0.593–0.613 Ma. The high-density plumes derived from the longer rivers of the southern rift that were prevalent before c. 0.593–0.613 Ma. When sediment is supplied as hemipelagic deposition, the proportion of the total grain-size population that is in the 0.3–0.5 µm range becomes an index for suspension fall-out deposits. The core shows coarser sediments during the marine periods, and this may be linked to the current circulation related to the Ishtmia Strait opening. The study thus illustrates how the establishment of interbasinal straits can influence the details of sedimentary hydrodynamics in the deep-water axis of an adjacent depocentre.