Pd-1/Au-20@ZrO2 nanoreactors with the gold nuclei confined within zirconia shell and decorated with Pd were synthesized using an Au:Pd molar ratio of 20:1. The presence of even trace amounts of Pd on the gold nuclei surface, significantly enhanced catalytic activity of Pd-1/Au-20@ZrO2 nanoreactors in the 4-nitrophenol to 4-aminophenol transformation by four times compared to Au@ZrO2. In addition, the Pd-1/Au-20@ZrO2 nanoreactors remained highly stable during the reaction even under harsh conditions, i.e. without nanoreactors cleaning before the subsequent catalytic run, comparable with the stability of Au@ZrO2 nanoreactors. The presently proposed synthesis technique allowed to prepare nanoreactors of uniform structure even with relatively unstable bimetallic NPs (Pd/Au) as nuclei. [GRAPHICS] .