The biochemical oxygen demand (BOD) is critical for assessing water quality, linking the quantity of biodegradable organic carbon with pollution levels. Electrochemical biosensors have shown great improvements over traditional BOD measurement methods by offering the advantages of simplicity, rapid response, high sensitivity, and real-time monitoring. In this review, we discuss different types of BOD electrochemical biosensors, including oxygen electrode-, microbial fuel cell (MFC)-, and microbial electrolysis cell (MEC)-type sensors, focusing on recent advances in microbial community composition, electrode materials, and optimization approaches. Moreover, current challenges in developing effective electrochemical biosensors for BOD detection are presented to meet diverse sample needs.