There is a growing need for effective and inexpensive environmental monitoring strategies for assessing heavy metal contamination levels. We developed a set of bacterial biosensors to simultaneously detect multiple bioavailable heavy metals (As(III) and Hg(II)). The biosensors provide a choice of the two reporter systems, luxCDABE and gfp, combined with metal responsive regulatory elements (ars and mer for As(III) and Hg(II), respectively). The results showed that the induction of the luxCDABE-based constructs was more sensitive than that of the gfp-based constructs for the detection of As(III) and Hg(II). In addition, both the luminescent and fluorescent biosensors readily distinguished As and Hg concentrations in groundwater samples to meet the groundwater quality standards. Due to the potentially complicated chemicals present in environmental samples, using a set of bacterial biosensors with different reporter genes to simultaneously determine the bioavailable proportions of heavy metals is desirable.