Nucleic acid-based biosensors are typically used to detect DNA or RNA fragments of genetic importance. However, nucleic acids can also serve as binding partners for other molecules, including metal ions. This binding occurs through electrostatic interactions between metal cations and negatively charged DNA strands and through the specific binding of metal cations by donor atoms from the phosphate groups and nucleobases. Additionally, the ability of nucleic acids to form secondary structures is of particular importance, as the formation of secondary structures can modify the interactions with metal ions through shape-recognition effects. This article reviews electrochemical DNA sensors used for metal ion quantification. These devices are divided into three categories: sensors with receptor layers composed of double- stranded DNA (dsDNA), single-stranded DNA (ssDNA) or random-sequence oligonucleotides; sensors based on oligonucleotide sequences that show high selectivity toward particular metal ions; and sensors that employ DNAzymes with metal ion cofactors.