Pre-Quaternary paleoclimate studies in Australia mainly focus on terrestrial records from the southeastern part of the continent. IODP Expedition 356 drilled on the northwestern Australian shelf, yielding Miocene-Pleistocene paleoclimate records in an area where climate archives are scarce. Post-expedition research revealed a dry-to–humid transition across the latest Miocene and early Pliocene (start of the “Humid Interval”). However, the complex tectonic history of the area makes these interpretations challenging. Here, we investigate late Miocene to early Pliocene sediment cores from two sites that are only 100 km apart, but situated in two adjacent basins (Northern Carnarvon and Roebuck Basins). Combining lithofacies study, time-series analysis of NGR potassium content (K wt%), calcareous nannofossil abundance counts (N/g) and accumulation rates (N/cm2/kyr), as well as benthic foraminifera δ¹⁸O, this work disentangles the complex interplay between basin evolution and climate change between 6.1-4 million years ago (Ma).