We present new seawater Cd concentration and ε112Cd/110Cd from five depth profiles in the South Atlantic along the western boundary (48.86˚S-0.18˚S, GEOTRACES JC057). The vertical distributions of [Cd] and (ε112Cd/110Cd) vary antithetically, with a decrease (increase) at depths influenced by NADW and a slight increase (decrease) reflecting northward AABW flow. The Log[Cd]-ε112Cd/110Cd systematics exhibit two distinct trends: (1) in the upper 1000 m, samples fall along the ACC surface waters correlation [1], while (2) intermediate and deep waters lie between NADW and AABW. These trends distinguish biological cycling of Cd in the upper ocean from water mass mixing in the deep ocean. The mixing between isotopically-distinct NADW and AABW components agrees with the ε112Cd/110Cd-salinity correlation in deep waters and the excellent linear [Cd]-[PO4] correlation in the South Atlantic. These systematic variations in the deep Atlantic Ocean and the remarkable agreement of the Subantarctic profile in this study with that along the Zero Meridian [2], suggest Cd isotopes behave conservatively in global ocean deep waters. [1] Abouchami et al., EPSL, 2011 [2] Abouchami et al., GCA (in review), 2013