Water flowing from the Pacific Ocean into the Indian Ocean plays a vital role in regulating global thermohaline circulation. Both water basins are connected north of Australia through the Indonesian Throughflow (ITF) and south of Australia through Tasman Leakage (TL). The onset of Tasman Leakage was suggested in the Late Miocene, yet its dynamics on astronomical timescales remain unknown. Here, we present new neodymium (Nd) isotope data from ODP Site 752 (Broken Ridge, Indian Ocean) to trace TL since the Middle Miocene. Both Nd isotope and related stable carbon isotope can be used to distinguish the water masses/ocean circulation. These results therefore, reveal the dynamic of TL since the Middle Miocene.