This study aimed to determine the possible control of selected pathogenic and competitive fungi of A. bisporus by three nanosilver clay composites and establish the effective concentrations of the composites for inhibiting pathogens. Nanosilver (AgNPs) clay (zeolite, montmorillonite, and palygorskite) composites were synthesized by a microwave‐assisted surface functionalization technique, and various techniques characterized the products. Zeolite and montmorillonite composites showed uniformly distributed spherical AgNPs with an average size of 3.33 nm and 2.85 nm, respectively, whereas palygorskite presented agglomerated and unevenly distributed AgNPs. The influence of the various composites on 9 fungi, including strains of T. aggressivum f. aggressivum, L. fungicola, C. dendroides, and Mycogone sp., was determined in vitro at different concentrations. At 10 mg/mL, AgNP‐zeolite and AgNP‐montmorillonite inhibited 8 out of 9 pathogens, while AgNP‐palygorskite only inhibited 1 pathogen. The nanosilver clay composites tested against A. bisporus revealed no adverse effects on mycelial growth at any concentrations tested. This study confirms that AgNP‐zeolite and AgNP‐montmorillonite composites have effective antifungal properties and can be used as alternative fungicides against mushroom pathogens without affecting A. bisporus growth. However, further investigation is required to unravel the mechanism of selective antifungal activity observed in this study.