The increasing demand for wood with enhanced flame retardant characteristics in construction applications necessitates strategic interventions. This study explores the fire behaviour and chemical characterisation of Robinia pseudoacacia wood subjected to thermal modification and flame retardant treatments. Thermal modification was carried out at three different temperatures (160 °C, 180 °C and 240 °C). The fire properties of wood coated with Flame Gard (F), a commercial flame retardant, arabinogalactan (A), a natural flame retardant, melamine adhesive (MF) with ammonium polyphosphate (AP), nanosilica (NS), nanoclay (NC) (MF-AP-NS and MF-AP-NC) and arabinogalactan with AP, NS and NC (A-AP-NS and A-AP-NC), were assessed using cone calorimetry in terms of the weight loss rate, ignition time and heat release rate. The commercial flame retardant Flame Gard outperformed the natural and fortified flame retardants in terms of the weight loss rate, heat release rate (HRR) and ignition time (t ig ). Unmodified samples exhibited superior fire properties in terms of t ig and HRR compared to thermally modified samples. The peak heat release rate (kW.m − 2 ) and time to peak heat release rate (s) showed a moderate degree of dependency on the chemical constituents of the wood.