Objective: The aim of the present study was to assess the anti-Aspergillus activity of culture filtrate of Streptomyces sp. VITSTK7 and biologically synthesized Ag2O/Ag nanoparticles using the culture filtrate of VITSTK7. Material and methods: Silver nanoparticles were synthesized by biological reduction of silver nitrate using culture filtrate of Streptomyces sp. VITSTK7. The synthesized nanopaticles were characterized for surface plasma resonance peak, X-ray diffraction patterns, shape and size distribution. Inhibition of mycelial growth was used as an index of anti- Aspergillus activity of synthesized nanoparticles. Results: The synthesized nanoparticles were spherical shaped and monodespersive in nature and showed a single surface plasma resonance peak at 420. nm. X-ray diffraction patterns displayed typical peaks of crystalline silver oxide and size distribution histograms indicated production of 20-60-nm-size nanoparticles with average size of 35.2. nm. The synthesized nanoparticles showed anti- Aspergillus activity against Aspergillus niger, Aspergillus flavus and Aspergillus fumigatus with antifungal index in the range of 62-75%. Conclusion: Thus the bioconversion of Ag2O/Ag nanoparticles by Streptomyces sp. VITSTK7 could be employed to control Aspergillus pathogenesis. The results of this study suggest that the green synthesis of Ag2O/Ag nanoparticles using marine Streptomyces sp. VITSTK7 yielded 27.9nm sized particles with potential to act against pathogenic Aspergillus species. © 2013 Elsevier Masson SAS.