We reconstructed the Indian Monsoon variability of the Earth's strongest hydrological system, at International Ocean Discovery Program (IODP) Expedition 353 Site U1448 in the Andaman Sea over the interval 6.24 to 4.91 Ma. We used high-resolution benthic and planktic foraminiferal carbon and oxygen isotopes and Mg/Ca measurements of the mixed layer foraminifer Trilobatus sacculifer to reconstruct the isotopic composition of seawater (δ¹⁸Osw) and the gradient between planktic and benthic foraminiferal δ¹³C.