An isotope shift of 5 ppm per deuterium atom has been observed for the 59Co resonance of tris(ethylenediamine)cobalt(III) chloride ([Co(en)3]Cl3) and hexaamminecobalt(III) chloride([Co(NH3)6]Cl3) after exchange of hydrogen for deuterium. The upfield direction of the shift can be readily understood as changes in the ligand-field strength causing changes in the nuclear paramagnetic screening.