This study investigates the effect of thermo-mechanical densification on the fire behaviour of wood using cone calorimetry. Scots pine wood was thermo-mechanically densified from an initial thickness of 20 mm to target thicknesses of 14 and 10 mm and compared with non-densified specimens of the same thickness as well as non-densified 20 mm samples. For non-densified specimens, the time to ignition (TTI) remained nearly constant (18–20 s) across the investigated thicknesses, indicating thermally thick behaviour. In contrast, delayed ignition was observed for the specimens densified to 10 mm (the higher densification ratio), with TTI increasing to 28 s. While the first peak heat release rate (pHRR) remained comparable across samples, densification increased the time to the second peak heat release rate by up to 85% and its magnitude by approximately 9% relative to non-densified specimens of the same thickness (10 mm). Densification was found to alter the combustion behaviour of wood by modifying the thermal inertia of the material and the characteristics of the resulting char layer, thereby affecting the transport and release of pyrolysis gases and producing distinct effects at different stages of combustion rather than an overall enhancement of fire performance.