Research has been carried out to assess the impact of mold fungi on polymer composite materials based on polypropylene produced by Omsk Polypropylene Plant LLC and unrefined natural rubber produced in Vietnam, grade RSS-1. The amount of natural rubber varied up to 15% of the mass. The fungal resistance of the compositions to the following types of fungi was assessed: Aspergillus niger, Aspergillus terreus, Aspergillus flavus, Chaetomium globosum, Paecilomyces variotii, Penicillium funiculosum, Penicillium chrysogenum, Trichoderma viredens. The decrease in the weight of the samples after incubation depends on the content of natural rubber in the composition. With the content of natural rubber in the composition in an amount of 1%, the average weight loss is 0.4% by weight, and when the content of natural rubber is 15% by weight. already ~ 2% of the mass. Starting with the addition of natural rubber in an amount of 1% by weight, the growth of fungi occurs, and the degree of their development is characterized by points 3-5. The resulting compositions are biodegradable, susceptible to the action of fungi, and, therefore, the manufacture of materials based on them will be an environmentally friendly alternative for further use.