In order to investigate the history of coastal T. aduncus populations in northwestern Australian waters, we generated a genomic SNP dataset using a double-digest restriction-site associated DNA sequencing (ddRAD using ecoRI/MseI) approach. The resulting dataset consists of 112 individuals sampled from eleven coastal sampling sites from Cygnet Bay, W.A. to Shark Bay, W.A. as well as two offshore sampling sites sampled beyond the 50m depth contour in the Pilbara region, W.A.. Our demographic analysis indicated that the expansion of T. aduncus along the coastline began around the last glacial maximum and progressed southwards with the Shark Bay population being founded only 13 kya. Our results are in line with coastal colonization histories inferred for Tursiops globally, highlighting the ability of delphinids to rapidly colonize novel coastal niches as habitat is released during glacial cycle-related global sea level and temperature changes.