Emerging contaminants have induced severe risks to the aquatic environment, and the continuous accumulation of various residues has forced aquatic ecosystems to deteriorate. The accumulation of emerging contaminants through food chains eventually causes serious harm to human production activities and life safety. Therefore, effective trace detection of emerging contaminants is needed to ensure water quality and safety. Electrochemical sensors are outstanding for portability, simple operation, high sensitivity, low detection limit, and fast detection speed. They could be used for trace detection of emerging contaminants in liquid environments. This study presented the performance of various nanostructured boron-doped diamond electrodes for the trace detection of emerging contaminants. The diamond electrodes were modified in different ways, including nanostructure, tip curvature, surface terminal, and modification regulation. The effects of various modifications on the electrochemical properties of diamond electrodes were discussed. Moreover, key modification strategies were studied to improve the sensitivity, selectivity, robustness, and real water performance of diamond electrodes in trace detection of emerging contaminants. Specific examples included the detection of endocrine-disrupting chemicals (e.g., nonylphenol), antibiotics (e.g., minocycline and doxorubicin), and persistent organic pollutants (e.g., polychlorinated biphenyls). Diamond-based water quality sensors could detect, analyze, track, and manage emerging contaminants quickly at trace levels.