Endophytic fungi are symbionts that grow inside the plants without causing any apparent disease. The objective of this study is to synthesize silver nanoparticles (SNP) using the aqueous extract from the endophytic fungi Aspergillus sp. of Justicia beddomei and to evaluate its antimicrobial activity. The extract was obtained by inoculating previously grown Aspergillus sp. on PDB media for 3 days with agitation. The filtrate was added to silver nitrate solution and left in the dark for synthesis of SNP. The characterization was done by measuring absorbance in UV- Visible spectrophotometer. The antimicrobial assay was performed using agar well diffusion technique and the zone of inhibition was observed. The inhibitory action was observed to be less with the cell free filtrate extract. Hence SNPs proved to be a potent inhibitor of pathogenic organisms including both bacteria and fungi. The study opens a possibility for the green synthesis of SNPs using endophytic fungi that can be easily and economically prepared from the fungal extract.