Abstract <p>Affected plant growth and decline in yield arose an urgent need to introduce the environmentally friendly approach in sustainable agriculture. Exploitation of mycelial fungi products in crop improvement is a challenging innovation. Higher fungi, xylotrophic basidiomycetes are known to be the reservoirs of bioactive extracellular metabolites. Interaction of xylotrophic basidiomycetes’ exopolymeric substances with plants is unexplored. This is the first study to have found how the fungal extracellular polysaccharides (EPS) function in favor of potato plants. Moreover, EPS produced in binary fungal-bacterial cultures are examined in this respect. The effects of EPS on the morphophysiological and biochemical variables of potato plants under in vitro culture conditions were explored. Potato (<i>Solanum tuberosum</i> L. ‘Kondor’) plants were treated with EPS isolated from the submerged cultures of five basidiomycetes, both from fungal monocultures and their 25 binary cultures with phytobeneficial bacteria. In the resulting plant samples, the values of shoot length, number of nodes per shoot, fresh and dry biomass of both shoots and roots, the rate of lipid peroxidation, the content of hydrogen peroxide, total phenols, and photosynthetic pigments were measured. Most of the EPS preparations improved biomass yields, as well as the morphological parameters examined. EPS application decreased oxidative damage to lipids. Judging by its overall effect on the growth indices, redox system of potato plants and photosynthetic pigments accumulation, EPS from <i>Laetiporus sulphureus</i> and <i>Ganoderma lucidum</i> were shown to be the most beneficial compared to others. Phytostimulating EPS properties may present a prospect for improved potato cultivation technology.</p>