The modern global food production system relies heavily on a considerable input of phosphorus. Sustainable food and agriculture need integrated phosphorus management, especially in phosphorus-scarce and food-deficient countries. This study aimed to investigate the phosphorus requirements to meet the future food demand for a phosphorus-scarce and food-deficient country, Comoros, as a case study. With its rapid population growth, domestic food production is far from meeting the food demand in Comoros, and the country relies on imported foods to satisfy the national needs; it is currently a net food importer, an import-dependent nation. We first calculated the virtual and embedded phosphorus flows through food trade in Comoros, from 1991 to 2013, and then estimated the phosphorus requirements for the future food demand under two scenarios. We found that the total virtual and embedded phosphorus through imported food increased from 163,313 to 493,190.97 kg and 53,190.12 to 143,009.62 kg in 1991 and 2013, respectively. Whereas, the embedded phosphorus through exported food shifted from 2548.75 to 1334.5 kg in 1991 and 2013, respectively. In addition, the Self-Sufficiency Ratio (SSR) analysis found that Comoros’s SSR is far below 100%; it varied from 46.27% in 1991 to 29.70% in 2013, indicating that the capacity of domestic production to cover domestic consumption fell by 16.57% during that period. In terms of phosphorus requirements, Comoros will require approximately 3,003,435.09 kg of phosphorus to reach 90% of the SSR or 3,337,150.10 kg to achieve 100% of the SSR, by 2030. These amounts could allow farmers to domestically produce the entire volume of food crops and livestock products that would otherwise be imported from trade.