The fracture behavior of four Ce-TZP zirconia composites containing 8vol% alumina and 8vol% strontium hexa-aluminate was investigated. The composites exhibited different degrees of transformation toughening obtained by varying the amount of the CeO2 stabilizer and the sintering temperature. The strength was measured by 4-point bending (4PB) and piston-on-three balls (POB) methods Toughness and crack growth resistance (R-curve) were determined from Single Edge V-Notched Beam (SEVNB) and double torsion (DT) samples, and slow crack growth (SCG) curves were determined by DT method.Increasing the transformability of the composites enhanced their crack growth resistance and consequently, increased their resistance to SCG, which was completely inhibited for the most transformable composites. Simultaneously, flaw tolerance was also improved although a decrease in strength was observed. Under all configurations, the composites exhibited a plastic behavior and it was shown that their properties are correlated to the crack shielding due to autocatalytic phase transformation that not only depend on the material transformability, but is also strongly influenced by the testing method.