Silver nanoparticles (AgNPs) were biosynthesized using the aqueous extract of Chayote fruit that served as both reducing and capping agents. The growth of AgNPs mostly occurred during the nucleation, and afterward, the natural capping agents inhibited AgNPs destabilization. The particles were of bi‐crystalline in nature with the predominant face‐centered cubic crystal of AgNPs with more than 99% yield within 24 h of reaction. The hydrodynamic diameter of AgNPs was around 1.6 times greater than the dry particles from TEM images. AgNPs were tested for the inactivation of Bacillus subtilis and Escherichia coli bacteria using the disc diffusion method. Furthermore, AgNPs were found to be highly effective against pathogenic fungi Aspergillus thermomutans. The free radical character of AgNPs caused the microbial inactivation. The synthesis route of AgNPs reported here is rather an ecofriendly, energy‐saving and faster than many conventional techniques and, the biosynthesis process didn't need any additional chemicals apart from the metal precursor. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 192–199, 2017