Although long-term studies on enhanced biological phosphorus removal systems and biofilm-based phosphorus enrichment processes have established the crucial involvement of extracellular polymeric substances (EPS), the mechanisms by which EPS participate in phosphorus uptake and release remain debated. Key points of contention include whether EPS exhibit independent phosphorus sequestration and release capabilities distinct from cellular metabolic activities, and whether biochemical reactions or physico-chemical precipitation processes dominate within EPS. This review summarizes major findings from previous research on phosphorus uptake and release mechanisms mediated by EPS. Based on the transport and transformation behavior of phosphorus and its compounds in environmental systems, as well as critical phenomena recently observed in sequencing batch biofilm reactors for phosphorus removal and enrichment, a new hypothesis is proposed: under redox-regulated conditions, the dominant mechanism of EPS in biological phosphorus cycling involves physico-chemical processes of binding/fixation and dissociation/mobilization, while phosphorus migration between EPS and the aqueous phase is primarily diffusion-driven. This hypothesis offers an integrated framework for explaining phosphorus translocation and transformation between EPS and the solution, helps to reconcile existing controversies and unanswered questions in the literature, and provides a novel theoretical basis for understanding the role of EPS in biological phosphorus removal processes.