Electrochemical carboxylation of (E)- and (Z)-beta-bromostyrenes (1) under an atmospheric pressure of carbon dioxide with a platinum cathode and a magnesium anode in the presence of 20 mol % of NiBr2 center dot bpy proceeded with retention of stereochemistry to give the corresponding (E)- or (Z)-cinnamic acids (2). The stereochemical outcome of nickel(II)-catalyzed electrochemical carboxylations was discussed by comparison with predominant formation of a (Z)-isomer from either (E)- or (Z)-beta-bromostyrenes.