<p>The sediments of coastal lagoons (CLs) display interlinked phosphorus (P) and trace metals sorption. CLs offer a wide variety of ecological services to the surrounding populations, but they also receive high loads of P and other potentially hazardous chemicals from human activities. However, there is a lack of information on (i) how the P sorption capacity of calcareous sediments could buffer degrading processes in CLs (e.g., eutrophication) located in tropical zones (e.g., the Caribbean Sea), and (ii) to what extent such buffering is affected by the presence of iron (Fe) and manganese (Mn). Thus, this research assessed the capacity of sediments to sequester P in two CLs located on the northern coast of Venezuela by calculating the Index of Bache and Williams (IBW) for P sorption. The link between P sorption and the geochemical partitioning of Fe and Mn was also evaluated in both CLs. IBW values indicate that sediments have low to moderate P sorption capacity. Fe and Mn were mainly bound to highly redox-reactive mineral phases such as crystalline (oxyhydr)oxides and sulfides, but IBW was correlated with Mn oxides and sulfides rather than Fe oxyhydroxides. This suggests that changes in environmental redox conditions could fuel the co-precipitation of P with Mn mineral phases in calcareous CLs. Thus, management strategies to mitigate high P loads could rely on boosting Mn cycling by, for example, increasing the amount of reactive Mn oxides in these environments. Overall, exploring Mn dynamics and its role in P sequestration in estuarine calcareous sediments is a research gap that needs more attention when evaluating P retention in shallow calcareous CLs in the Caribbean Sea and other tropical zones.</p>