Biological activities of medicinal mushrooms have been attributed to β-(1→3),(1→6)-glucans that are present in the cell wall of fungi and some plants. Antitumor, immunomodulatory, antimicrobial, antinociception, antiinflammatory, prebiotic, antioxidant, and antidiabetic are some of different properties already described for β-(1→3),(1→6)-glucans. Immune activation systems, including specific β-glucan receptors like Dectin-1, complement (CR3), and Toll (TLR), have been identified to clarify these biological effects. The β-(1→3)-glucans are synthesized by β-(1→3)-glucan synthase (GLS), an enzyme belonging to the glucosyltransferase group, which has a catalytic unit (FKS) and another regulatory (RHO). The mechanisms for adding β-(1→6) branches to the non-reducing ends of the β-(1→3)-glucan chains are unclear until now. Due to the biological importance of β-(1→3),(1→6)-glucan, it is necessary to understand the biochemical and molecular mechanisms of its synthesis, both to optimize the production of bioactive compounds and to develop antifungal drugs that interrupt this process. Therefore, the aim of this review is to gather information about the potential of β-(1→3),(1→6)-glucans, their methods of isolation, purification, and chemical characterization, as well as how these biomolecules are synthesized by fungi and what studies involving biotechnology or molecular biology have contributed to this subject.