The large-scale use of organophosphate esters (OPEs) as flame retardants and plasticizers has led to their prevalence in the environment, with still unknown broader impacts. This Review describes the transport and occurrence of OPEs in marine systems and summarizes emerging evidence of their biogeochemical and ecosystem impacts. Long-range environmental transport via the atmosphere and ocean currents distributes OPEs from industrialized regions to the open ocean. OPEs are most prevalent in coastal regions, but notable concentrations are also found in the Arctic and regions far from shore. Air–water interactions are important for the transport of OPEs to remote oceans and polar regions. Processes such as degradation and sinking of particle-bound compounds modulate the properties and fate of OPEs in the water column, where they are potentially a non-accounted source of anthropogenic organic phosphorus for microbial communities. Some OPEs have toxic effects in marine species and are found in measurable quantities in fish and other aquatic organisms. However, there is conflicting evidence on the potential for bioaccumulation and biomagnification of OPEs. Future work must constrain the large-scale impact of OPEs on marine biota and biogeochemistry to support more effective regulation and mitigation.