From long time ago, the use of silver nanoparticles to control the growth and prevalence of disease causing bacteria is well known. In recent times, bacteria make themselves resistant to varied antibiotics based on their genes present in the plasmids. During the present study, an effective approach was performed to synthesize potent silver nanoparticles (AgNPs) from two mould fungi; Alternaria sp. and Alternaria alternata. The appearance of yellowish brown color in the conical flask suggested the formation of AgNPs. The extract of the fungus culture changed the solution into brownish color during the reaction. The characterization of silver nanoparticles was confirmed by Uv- Vis spectroscopy, Field emission scanning electron microscopy (FESEM). Size of the nanoparticles measured between 20nm to 30nm by FESEM. The synthesized silver nanoparticles were subjected to their characterization by X-ray diffraction (XRD) technique to determine the metallic nature of nanoparticles. The XRD analysis confirmed that silver nanoparticles have been formed resulting in the diffraction peaks at 38, 45, 64 and 77 respectively showing the metallic nature of nanoparticles and peak were specific for the silver nanoparticles. Silver nanoparticles synthesized from both the fungi showed good antimicrobial activity against the selected bacterial pathogens like, Staphylococcus aureus, Bacillus cereus, Proteus vulgaris, E. coli and Vibrio cholerae and the nanoparticles were found more effective against the test pathogens in combined with the available drugs viz., Amoxicillin (30mcg). The efficacy of the drugs was increased at high level of potency.