Wood is a very aesthetically pleasing and environmentally friendly material that can be used both indoors and outdoors. Many research teams are now paying closer attention to polymer modification using furfuryl alcohol or biochar because of its potential for commercial applications. It is anticipated that this kind of material will be long-lasting and maintain its mechanical properties over time. In this paper, spruce wood was modified by a furfuryl alcohol solution enriched by biochar using vacuum infiltration. Therefore, the purpose of this work was to investigate whether spruce wood was suitable for this treatment and to evaluate the effects of thermal degradation properties on prepared composite. Thermogravimetric analysis of raw wood (W), furfurylated wood (FW), and biochar-furfurylated wood bio-composite (BFW) reveals significant differences in its thermal stability. Wood exhibits the lowest thermal stability due to its composition. BFW showed higher thermal stability than wood. FW decomposes similarly to BFW but shows higher mass loss at low temperatures. The obtained results proved increasing two key fire characteristics (decrease of effective heat of combustion and carbon monoxide yield) of BFW in comparison with pristine spruce wood.