Herein, we report the production of novel organic-inorganic nanobio-catalytic and antimicrobial agents called "nanosnowball" (NSBs) with a rational design and elucidate the increase in the catalytic and antimicrobial activities. The NSBs resemble to guelder rose were formed of the extract of Viburnum opulus (VO) as the organic component and copper (II) ions (Cu2+) as the inorganic component. The effects of the VO extract and Cu2+ concentrations on the morphology of NSBs were systematically examined and characterized with several techniques such as SEM, FT-IR, EDX and XRD. Our results demonstrated that the presence of Cu-O bonds in NSBs could be indication of VO extract-Cu2+ complexes. Interestingly, the NSBs exhibited peroxidase-like activity towards guaiacol used as a model substrate depending on Fenton-like reaction. While free VO extract did not show antimicrobial activity at indicated concentration (2000-125 mu g/mL), the NSBs showed effective antimicrobial activity against bacterial (Escherichia coli ATCC 35218, Salmonella typhi ATCC 14028, Enterococcus faecium ATCC 8459, Enterococcus faecalis ATCC 29212, Bacillus cereus ATCC 11778, Staphylococcus aureus ATCC 25923, except Pseudomonas aeruginosa ATCC 27853 and Haemophilus influenza ATCC 49247) and fungal pathogens (Candida albicans ATCC 10231, C. glabrata ATCC 90030), respectively.