Global industrialization and agricultural development are related to the release of various pollutants into the environment including huge amounts of free radicals, which are associated with the occurrence of various destructive diseases and disorders. Due to different rates of metabolic activity and oxygen consumption, organisms, organs and tissues have distinct protective antioxidant systems and defence mechanisms. Although numerous synthetic antioxidants can improve defence system capacity, because of their toxic and mutagenic effects as well as rising awareness of a healthy lifestyle, preference is given to natural antioxidants. Therefore, studies of metabolites of various fungal species and their activity are currently increasing. Antioxidant features of numerous compounds isolated from mushrooms, such as phenolic compounds, vitamins, polysaccharides, peptides, proteins, organic acids, carotenoids, alkaloids, and nucleotides, have been reported. Chemical composition and antioxidant potential of mushrooms are highly-dependent on species, habitat, phase of life cycle (mycelium, young or mature fruiting body), method of processing, extraction solvent, and extract dose. Although around only 5% of fungal species have been well studied and thousands more species have potential benefit for mankind, reports on the antioxidant potentials of fungi are already numerous and these are the subject of this review.