Plasmid‐encoded mercuric reduction involves transfer of Hg2+ across the cellular envelope and reduction to Hg0 by the cytoplasmic mercuric reductase using NADPH. A mathematical model was developed for the binding and transfer of Hg2+ by transport proteins and the subsequent reduction of Hg2+. The values of the model parameters were determined using experimental data. The derived rate expressions were similar to the previously experimentally determined ones. The model predicted that a differential amplification of the transport protein relative to mercuric reductase expression levels may enhance the Hg2+ reduction rate in whole cells.