Wood modification using melamine formaldehyde (MF) resin has been recognized for its efficacy in enhancing the resistance against wood-destroying organisms and reducing moisture-induced swelling and shrinking processes. However, this treatment shows a low impact on the flammability and combustion behavior of wood. To address the aspect of fire protection, one approach could be a combination of MF resins with compatible flame retardant agents. In this study, Scots pine sapwood (Pinus sylvestris L) has been treated with an aqueous MF resin formulation, to which a phosphorus polyol was added. Both, the fixation of the flame retardant (FR) inside the wooden structure and the fire performance were studied on treated wood specimens. The fixation of the FR was assessed by weight percent gain with an accelerated ageing process according to EN 84 (2020). The reaction to fire of the treated material was assessed through the Bunsen burner test and mass loss calorimeter measurements (ISO 13927). Results indicated that MF and FR can penetrate the wood cell wall and be deposited inside the wooden structure. After an accelerated ageing process (EN 84), pure flame retardant treatment does not fix the flame retardant, while a certain fixation could be achieved by the incorporation in a polymeric network formed by cured MF resin. The combined treatment of MF + FR demonstrated a significant improvement in flammability and reduction in heat release. After the leaching process, the THR600s values for MF + FR treated wood (9.9 MJ/m2) exhibited an 80% reduction compared to untreated wood (48.5 MJ/m2).