Mold invasion by Trichoderma harzianum T6776 over the surface of wood-plastic composites (WPCs) made from Juniperus procera wood-branch and polypropylene with a melt-blending technique was examined using scanning electron microscopy (SEM) and electron dispersive X-ray spectroscopy (EDX). Before the addition of coupling agent, the WPC samples were made from untreated and pretreated wood-branch particles of J. procera with either cold or hot water and then mixed with polypropylene to produce panels. The surfaces of WPC samples were inoculated by a mold suspension of T. harzianum. SEM-EDX measurements of WPCs made from J. procera particles showed little or no growth of T. harzianum, irrespective of treatment with cold or hot water. The results suggest that WPCs made from the particles of J. procera wood-branch pretreated with either cold or hot water could be useable in wet conditions. In addition, using of J. procera as durable wood for manufacturing of WPCs had good effects on the prevention of the mold infestation over the surfaces of the produced panels.