The dimensional stability and resistance to degradation of wood can be improved using high temperature heat treatment under anaerobic conditions; however, mildew growth can have a deleterious impact on its appearance and commercial value. In this study, wood samples were impregnated in copper-containing solutions at high pressure before being recovered and cured at high temperatures to create treated wood samples with nano copper particles. This copper impregnated wood (up to 6.35% copper content) suppressed the growth of Botryodiplodia theobromae Pat. and Aspergillus niger van Tieghem with 100% efficiency, and Penicillium citrinum Thom with 75% efficiency. However, the growth of Trichoderma viride Pers. was not suppressed. These results demonstrate that copper curing can be used to extend the scope, performance, and lifetime of heat-treated wood, enabling it to be used for a new range of applications.