This study aimed to assess the efficacy of formaldehyde-free tannin-hexamine-boric acid resin, in comparison with melamine-formaldehyde resin, for enhancing the biological resistance of ancient oak wood (Quercus castaneifolia) copings against white rot fungus (Trametes versicolor), brown rot fungus (Coniophora puteana), and the underground termite (Reticulitermes flavipes). The wood specimens were impregnated with the resins through a full cell process, followed by drying according to a moisture-based schedule, curing of the resin at 103¿±¿2 °C for 48¿h, and eventually a 4-hour curing period at 120 °C. The weight percent gain (WPG) was notably higher for the samples impregnated with melamine-formaldehyde resin (15.5¿%) compared to those impregnated by formaldehyde-free tannin-hexamine-boric acid resin (7.4¿%). No significant discrepancies were observed in leaching resistance among the two resin types. The results revealed that the resins were more effective in enhancing the resistance of ancient wood to termites than to fungi.