A fungal strain, KSU-09, isolated from the roots of date palm (Phoenix dactylifera), was identified as Amylomyces rouxii based on sequence analysis of the internal transcribed spacer (ITS) region of its rRNA genes. Mycelia-free water extracts obtained from mycelium suspended in water for 72h facilitated the production of stable, predominantly monodispersed and spherical silver nanoparticles (AgNPs) in the size range of 5-27nm upon addition of 1mM silver nitrate, as determined by the XRD, AFM and TEM. The AgNPs exhibited antimicrobial activity against Shigella dysenteriae type I, Staphylococcus aureus, Citrobacter sp., Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Candida albicans and Fusarium oxysporum. Thus, the strain KSU-09 could be used for simple, non-hazardous and efficient synthesis of antimicrobial AgNPs.