Polyurethane (PU) foams are widely used for many applications, however the use of toxic isocyanate monomers for their synthesis has recently led researchers to non-isocyanate PU foams. The most promising alternative is the aminolysis of cyclic carbonate which yields polyhydroxyurethanes (PHU). Nevertheless, the obtained foams suffer from significant flammability and require the introduction of flame retardants to improve their flame retardant properties. Hence, this article demonstrates the first synthesis of PHUs foams containing phosphorus-based flame retardants. The flame retardant were allowed to react with the monomers to prevent any leaching from the foams. Moreover, several structures of cyclic carbonates were analyzed in order to determine the influence of aromatic rings on both thermal stability and mechanical properties of foams by thermogravimetric analyses, differential scanning calorimetry and dynamic mechanical analyses. The flame retardant properties were studied with a cone calorimeter and pyrolysis combustion flow calorimeter. The best results were obtained by the foam containing 2 wt% of phosphorus and two aromatic rings in the cyclic carbonate structure. Cone calorimeter analysis showed a total heat release of 13.1 KJ.g−1 versus 19.1 KJ.g−1 for the DOPO-free foam.