We present experimental evidence of complete fractal properties inheritance in the course of first-order phase transition from amorphous to monoclinic or tetragonal zirconia under hydrothermal conditions. This phenomenon takes place either under rapid microwave heating or conventional heating regardless of starting fractal dimension value. Exactly the same effect is observed for hafnia. The similarity of the local structures of amorphous and crystalline zirconia as well as relatively soft crystallization conditions could be the definite reasons for the conservation of the mesostructure in the course of phase transition.