The behaviour of hydrothermal degraded 3 % molar yttria stabilised zirconia under monotonic spherical indentation has been studied. The investigation is focused mainly on analysing the response under spherical indentation in terms of the transformed monoclinic surface layer that appears after hydrothermal degradation. The mechanisms of damage are ring and cone cracking, similarly as in as sintered specimens. The permanent damage induced in degraded specimens is always larger than in the as sintered specimens. The "plastic" damage measured by the value of the indentation strain in degraded specimens is larger than in as sintered specimens at the same indentation pressure. The critical contact load to induce ring cracking is determined and it is found that in degraded specimens its value is lower than in as sintered specimens. The results are discussed in terms of elastic properties and microstructure of the degraded layer.