The present study is concerned with the morphology, physical properties and biocidal activity of Al2O3-Ag nanopowders produced by two methods: thermal decomposition-reduction and the silver nitrate reduction. The innovative method of thermal decomposition-reduction has been described in our earlier publication and is protected by our patent application, whereas the silver nitrate reduction method is commonly used in industry at the present. The nano-powders produced by these two methods differ considerably from one another in terms of their morphology and physical properties. The proposed method of thermal decomposition-reduction gives Al2O3-Ag nano-powders which are not only much less agglomerated with the average agglomerate sizes below 1 µm, but also the average size of their particles is considerably smaller (below 60 nm). Moreover, their specific surface is larger (above 200 m2g-1) and they have good bactericidal and fungicidal properties.