The article presents the fire performance, the mechanical-physical properties of thermo-mechanical pulp (TMP) treated with P-N containing fire-retardants (FR), and MDF made out of it. Three P-N containing FR with different P-N ratios were used. The FRs were added to the fibres with two different loadings (10 % and 20 % dry salt on dry wood). In addition to the FR, three adhesive types were tested (mUF, PF, pMDI). The TMP modified with FR were characterised chemically (pH value, buffer capacity, C-N-P content) and thermo-gravimetrically (TGA). The fire properties of the MDF were analysed by cone calorimetry. All three FR lead to a significant reduction in heat release in both the fibres and the MDF, regardless of the P-N content. The FR content exerts the greatest influence on the fire properties. In the case of the three adhesives, the reduction in the mechanical properties is only satisfactorily counteracted by pMDI.