ABSTRACT Owing to the expensive and toxic nature of physical and chemical methods employed in the synthesis of commercially available metal nanoparticles used in wood protection, researchers are in search of non-toxic methods for nanoparticle synthesis. The present study involves biological synthesis of copper oxide nanoparticles using leaf extracts of Lantana camara L. and Nerium oleander L. The synthesised copper oxide nanoparticles were characterised using Scanning Electron Microscopy coupled with EDAX. The efficacy of formulations, containing leaf extracts and copper oxide nanoparticles, is screened against wood decay fungi Trametes hirsuta (White-rot) and Oligoporus placenta (brown-rot). Similarly, the efficacies of CuSO4. 5H2O (0.5%), CuO (0.5%) nanoparticle and CuO (0.5%) were also tested. Results indicated that the formulation of Lantana camara leaf extract and CuO nanoparticles effectively protected the treated rubberwood from the attack of both white-rot and brown-rot, whereas the formulation of Nerium oleander leaf extract and CuO nanoparticles protected from brown-rot attack only. Since test chemicals and leaf extracts alone were not effective against decay fungi, the protective effect of the formulation can be attributed to the synergistic effect of the intrinsic property of leaf extracts and the biocidal property of copper oxide nanoparticles resulting in an effective wood protectant.