Sediment microbial fuel cells (SMFCs) have been intensively investigated for the harvest of energy from natural sediment, but studies of their application for wastewater treatment mainly occurred in the past 2–3 years. SMFCs with simple structures can generate electrical energy while decontaminating wastewater. Most SMFCs used for wastewater treatment contain plants to mimic constructed wetlands. Both synthetic and real wastewaters have been used as substrates in SMFCs that achieved satisfactory performance in organic removal. SMFCs have also been scaled up from several litres to more than 150 L. To further develop this technology, identification of a suitable application niche is needed. Several challenges must be addressed, including more detailed analysis in energy production, consumption, and application, understanding the relationship between electricity generation and contaminant removal, selecting plants that will benefit electrode reactions, improving nutrients removal, and optimizing system configuration and operation. The potential applications of SMFCs for wastewater treatment include powering sensors to monitor treatment processes and enhancing the removal of specific contaminants by electricity generation.