The objective of present study was to produce mullite-zirconia nanostructured composite by mechanical activation of zircon-alumina powder mixture followed by reaction sintering. The results showed that mechanical activation up to 60 h led to no phase change. Complete formation of mullite-zirconia composite was observed after 60 h of mechanical activation and subsequent reaction sintering at 1400 degrees C for 2 h. This temperature is about 200-250 degrees C lower than the temperatures commonly used in the reaction sintering of zircon-alumina powder mixture. Density measurements showed that the relative density of green bodies was similar to 78%, which increased to values above 90% after reaction sintering. It was also observed that the relative density of reaction sintered samples increased with an increase in the mechanical activation time. The produced composite showed a hardness value of 11.1 GPa, which is comparable with the hardness value of mullite-zirconia composites obtained by other methods. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.