Ecosystem pollution by mercury ions (Hg) is a major health concern, yet classical analytical methods for mercury analysis are limited. This paper reviews the advances in Hg detection using DNA as recognition elements in the sensors. DNA as a recognition molecule is inexpensive, simple, and appropriate for real-time detection of Hg. This paper discusses the DNA-based sensors that were used for the detection of Hg. These can be carried out by electrochemistry, field effect transistors (FET), Raman spectroscopy, colorimetry, and fluorescence resonance energy transfer (FRET). The detection principles and the advantages of DNA in these sensors are also revealed. Finally, the paper provides an overview of prospects and potential challenges in the field.