Spark Plasma Sintering (SPS) method was practiced, in the current investigation, to obtain fully dense materials with an excellent dispersion of MWCNTs (Multi-walled Carbon Nanotubes) within the matrix. Scanning and transmission electron microscopy micrographs as well as Raman Spectroscopy revealed no conspicuous signs of damages on the nanotubes' structure, as a result of applying appropriate processing measures. Measurements of mechanical properties' revealed the value of 15.2 +/- 0.4 MPa m(1/2) for indentation fracture toughness, impling our success to align transformation toughening (while the zirconia has the grain size around 1 mu m) with the effects of MWCNTs addition (5 wt%). High temperature mechanical properties of the composites have been investigated using Mechanical Spectroscopy (MS) up to 1600 K at frequency equal to 1 Hz. The MS results proved that CNTs could hinder grain-boundary sliding and subsequently lead to an enhanced creep resitance at high temperatures. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.