We reconstruct the evolution of deep-water chemistry across the Miocene Climate Optimum (16.9 to 14.7 Ma) and Middle Miocene Climate Transition (14.7-13.8 Ma), using high-resolution benthic foraminiferal stable isotopes, X-ray fluorescence (XRF) scanner-derived elemental records, light reflectance spectroscopy data as well as coarse fraction >63 µm residue and calcium carbonate (CaCO3) weight percentage records from western equatorial Pacific Site U1490. We integrate our results with published records from key locations in the Pacific, Indian and Southern Oceans to investigate ocean-wide circulation changes and to better understand the processes driving short- and long-term variations in deep water production and ocean overturning on a warmer-than-modern Earth.