Mercury is toxic with widespread contamination. Highly sensitive and selective approaches for mercury analysis are desired. Although conventional techniques are accurate and sensitive in the determination of mercury, these procedures are time-consuming, labor-intensive and dependent heavily on expensive instrumentation. In recent years, nanomaterial-based approaches have been proved to be effective alternatives in the detection and speciation of mercury. In this review, the development of different nanomaterial-based approaches was summarized, as well as their utilization for the detection of mercury in environmental and biological samples, such as gold nanomaterials, carbon nanomaterials, quantum dots and so on. Moreover, the speciation of mercury using nanomaterials was also reviewed.