The massive production, consumption, and (improper) recycling/disposal of electronic device/waste (e-device/e-waste) will release numerous hazardous substances into the environment. Liquid crystal monomers (LCMs) are the displaying materials used in the manufacture of liquid crystal display (LCD) panels. LCMs have been proposed as an emerging class of chemicals of concern related to e-waste, which were recently detected in indoor dust and sediment samples collected near e-waste recycling facilities. They are potentially persistent, bioaccumulative, and toxic (PBT) substances and may threaten the aquatic ecosystem. Currently, limited information is available for analytical methods, occurrence, distribution, and ecological risk of LCMs, especially in the marine/coastal ecosystems. Our group has developed robust methods to determine a list of target LCMs in complex environmental matrices. We have determined the presence of LCMs in municipal landfill leachate collected from Hong Kong and Shenzhen and also discovered a widespread occurrence of LCMs in the sediment samples collected from the Peral River Estuary (PRE). The obtained results showed that the levels of LCMs are similar, or even higher, compared to other legacy and emerging organic pollutants (e.g., PAHs, PBDEs, PFASs) found in the same area. Given the fact that the PRE receives organic contaminants discharged from the Pearl River Delta region, where primitive handling of e-waste is common, the current contamination status of LCMs might be alarming, and further investigation of the ecological impact of LCMs on the marine ecosystem, as well as identification of their sources and control measures are urgently warranted.