Abstract Extensive evidence for submarine landslide failure is found along the east Australian continental margin. This paper assesses the sedimentological properties and models the failure event that created the Byron landslide scar, located on the SE Australian continental margin, c. 34 km off the coast of Byron Bay, New South Wales. Sedimentological analyses and dating (radiocarbon and biostratigraphic) were conducted on three gravity cores collected from within the Byron landslide scar. A paraconformity, identified in one of the three cores by a distinct colour change, was found to represent a distinct radiocarbon age gap of at least 25 ka and probably represents the detachment surface of the slide plane. The core-derived sediment properties for the Byron landslide scar were used to inform hydrodynamic modelling using the freely available numerical modelling software, Basilisk. Model results highlight the important role of sediment rheology on the tsunamigenic potential of the slide and on the resulting inundation along the east Australian coastline, therefore providing a greater understanding of the modern hazard posed by comparable future submarine landslide events for the east Australian coastline.