The main objective of this study was to determine the durability of chemical preservatives treated wood flour/high density polyethylene (HDPE) composites to white-rot fungus (Coriolus versicolor). Specimens, containing treated and untreated poplar wood flour (PF, 60%), were mixed with HDPE (38%) as polymer matrix and maleic anhydride grafted polyethylene (MAPE, 2 wt.%) as coupling agent. Two fungicide materials, namely 3-iodo-2-propynyl butylcarbamate (IPBC, 0.3, 0.6 and 0.9 wt.%) and 2 thiazol-4-yl-1H-benzoimidazole (TBZ, 0.3, 0.6 and 0.9 wt.%) were used in preparation of wood plastic composites (WPCs). Then, treated and untreated composites were exposed to the fungal decay for 12 weeks according to the European Union (EN) 113 standard. Mechanical and physical properties of the composites were evaluated before and after fungal incubation. The experimental results indicated that treated composites were more resistant to decay, with strength losses significantly lower than the untreated (control) sample. Physical properties in terms of water absorption and thickness swelling were improved by the incorporation of fungicide agents, but no significant differences were observed between the treaded samples. Weight losses for the various treated composites ranged from 1.1% to 4.5%. In addition, IPBC treated samples showed slightly lower weight loss compared with the treated composites with TBZ. The highest weight loss corresponds to the control. Accordingly, IPBC and TBZ can be effectively used as preservatives for WPC. However, IPBC showed superior results compared to the TBZ and it is recommended for the WPCs preservation.