The ear- to shell-shaped fruiting bodies of the genusAuriculariaare widely used as food and in traditional medicinal remedies. This study was primarily focused on the composition, properties and potential use of the gel-forming extract fromAuricularia heimuer. The dried extract contained 50% soluble homo- and heteropolysaccharides, which were mainly composed of mannose and glucose, acetyl residues, glucuronic acid and a small amount of xylose, galactose, glucosamine, fucose, arabinose and rhamnose. The minerals observed in the extract included approximately 70% potassium followed by calcium. Among the fatty and amino acids, 60% unsaturated fatty acids and 35% essential amino acids could be calculated. At both acidic (pH 4) and alkaline (pH 10) conditions, the thickness of the 5 mg/mL extract did not change in a temperature range from −24 °C to room temperature, but decreased statistically significantly after storage at elevated temperature. At neutral pH, the studied extract demonstrated good thermal and storage stability, as well as a moisture retention capacity comparable to the high molecular weight sodium hyaluronate, a well-known moisturizer. Hydrocolloids that can be sustainably produced fromAuriculariafruiting bodies offer great application potential in the food and cosmetic industries.