Microbial electrolysis cells (MECs) have been studied in a wide range of potential applications such as recalcitrant pollutants removal, chemicals synthesis, resources recovery and biosensors. However, MEC technology is still in its infancy and poses serious challenges for practical large-scale applications. To understand the diversified applications of MEC, this review aims to explore MEC applications in the following contexts: an overview of MEC for energy generation and recycling such as hydrogen, methane, formic acid and hydrogen peroxide; contaminant removal, specifically complex organic pollutants and inorganic pollutants; as a sensor; as well as resource recovery. New concepts of MEC technology; configuration optimization; electron transfer pathways in biocathodes, and coupling with other technologies for value-added applications such as MEC-anaerobic digestion, MEC-MFC, MEC-MDC and bio-E-Fenton system are discussed. Finally, challenges and outlooks are suggested. The review aims to assist researchers and engineers to understand the latest trends in MEC technologies and applications. (c) 2018 Society of Chemical Industry