Dissimilatory nitrate reduction to ammonium (DNRA) of bacteria is a potentially important path of nitrogen cycling in estuarine regions. This paper introduces the mechanisms and types of DNRA, reviews the value and impacts of DNRA, and summarizes the influence of several major environmental factors on DNRA in estuarine regions. Parts of the mechanisms of DNRA still remain unclear. Further studies focusing on the relationship between DNRA and environmental factors, as well as the development of new methods and techniques are suggested, to provide a scientific basis for the protection and restoration of estuarine regions.