Crude polysaccharide extracts derived from Agaricus bisporus (A), A. brasiliensis (B), and Phellinus linteus (P) were used for the synthesis of silver nanoparticles (AgNPs, labeled AAgNP, BAgNP, PAgNP, respectively). UV and FT-IR spectra, size distribution, and zeta potential of the respective particles were recorded, and TEM and SEM-EDS characterization was done. UV-Vis spectroscopy showed maximum absorbance at 415 nm for A, at 400 nm for P, and at 420 nm for B. SEM-EDS analysis showed BAgNP to consist of almost 90% of silver, while silver content in AAgNP and PAgNP was much lower, 46.5 and 52.3%, respectively. Individual extracts as well as the Ag-NPs were tested against a panel of clinically isolated and ATCC derived pathogens. In almost all cases minimum inhibitory concentration (MIC) was significantly lower than those of antibiotics, suggesting up to 100 times more effectivity. BAgNP, PAgNP, and AAgNP appeared very active against Pseudomonas aeruginosa ATCC 27853 (MIC: 0.19, 0.19, 0.97 μg/mL, respectively). The same nanoparticles were also very effective toward Candida albicans ATCC 10231 (MIC: 0.39, 0.78, 0.97 μg/mL, respectively). Our study indicates that the bactericidal effect of PAgNP, AAgNP, BAgNP on E. coli 25922 ATCC (MBC: 1.56, 0.97, 6.25 μg/mL, respectively) is significantly more pronounced than that of amoxicillin. A pure solution of colloidal silver nanoparticles showed significantly weaker microbiostatic/microbiocidal potential than all tested mushroom extracts' AgNPs, as well as amoxicillin. Silver nanoparticles made with extracts of A, B, and P seem welcome as an addition to the inventory of antimicrobial compounds used in clinical medicine against bacterial and yeast infection.