The effects of inelastic deformation, in the form of plastic and creep pre-strain, on the fracture toughness behaviour of Type 316H stainless steel have been investigated in this study. Material pre-conditioning effects on the strain distribution fields ahead of the crack tip have been investigated using digital image correlation technique. Fracture toughness tests have been performed on compact tension specimens made of the as-received, plastic pre-strained and creep pre-strained materials. The influences of specimen side groove and pre-cracking type on the fracture toughness behaviour of 316H stainless steel have also been examined. The test results have shown that the fracture toughness values decrease by increasing the percentage of inelastic pre-strain introduced into the material. Moreover, the generated R-curves and the subsequent fracture toughness values have been found sensitive to the specimen side groove. Finally, it has been observed that local creep damage has more severe impact on the fracture toughness of the material compared to global creep deformation.