The Eastern Tropical North Atlantic Oxygen Minimum Zone (OMZ) is a biogeochemically important area near the Cape Verde Islands. The low oxygen in this region is thought to be maintained by a balance between the slow mixing supply of O2 and its removal by respiration. We use data collected from 90 isopycnal RAFOS floats to characterize the mixing coefficients responsible for the supply of oxygen to the region. One group was ballasted to drift on the isopycnal where oxygen is at its minimum, and the other group about 300 m deeper. Using the record of the float positions at each 6-hr interval, we calculate the relative dispersion of a large number of pairs of floats. The time derivative of this dispersion provides a diffusivity coefficient that captures the net effect of eddy driven mixing along each isopycnal. With its sluggish mean circulation, the OMZ provided a study area in which this isopycnal mixing is observed with little interference by background advection. Relative dispersion of the floats in the OMZ area obeyed the canonical 4/3rds power scaling, representative of two dimensional turbulence. At the length scale of the maximum energy containing eddy, the effective diffusivity is 1400 ± 500 m2 s-1 in the zonal direction and 800 ± 300 m2 s-1 in the meridional. Within our quantification of error, the diffusivities on the two isopycnals are indistinguishable from one another. Synthesis of the diffusivity results suggest that meridional mixing across the large-scale O2 gradient is the leading supply term of oxygen to the OMZ.