Nanostructured materials with a nanosized dispersed phase have supposed a conceptual revolution in the field of ceramic-ceramic composites. The inclusion of a secondary phase, even in small quantities into a matrix allows enhancing the toughness and fracturing strength of the matrix. This is the case of the ZTA composites (zirconia-toughened alumina, ZTA) where the secondary phase of zirconia controls the matrix grain size and provides toughening through a phase transformation mechanism. In the present work, ZTA composites with 5vol% of nanosized, un-doped tetragonal ZrO2 synthesized by freeze-drying have been prepared by an aqueous gelcasting process. Gelcasting was performed using a glycerol monoacrylate monomer synthesised in the laboratory, which allows obtaining near-net-shaped bodies with homogeneous microstructure without crosslinking agent. The stability of nanozirconia and submicrometric alumina was studied in terms of zeta potential and rheological measurements. The samples were characterized by SEM and density measurements, being the zirconia nanoparticles in the triple point between the alumina grains preventing exaggerated grain growth. Mechanical response was evaluated by indentantion tests. Composites prepared from bimodal suspensions containing nanometric and submicronic particles were studied in terms of rheological behaviour, density and microstructure and the results compared to those of the studied ZTA composites.