The fracture toughness and hardness of Ce–Y–TZP ceramics with various compositions are studied by using Vickers indentation. It is found that crack mode of Ce–Y–TZP belongs to Palmqvist crack under loads ≦490 N. The hardness is enhanced with increasing mol% YO1.5, while this trend is depressed with the increase of CeO2 content. Samples with compositions located in the vicinity of t→m boundary tend to possess higher toughness. The closer the compositions near t-phase boundary of t–m, the higher the fracture toughness of Ce–Y–TZPs due to the increase of transformability or operation of relevant toughening mechanisms. As temperature and tetragonality of t-phase are regarded as the ease of degree in the t→m transformation, and the relation between As temperature and tetragonality with K1c value are further explored.