The present invention relates to protease variants, having improved properties compared to the parent protease, in particular variants of a serine protease belonging to family 53 derived from a strain of Meripilus giganteus. The variants according to the invention have in particular increased thermo-stability, e.g., increased residual activity after 30 min at a temperature in the range from 55 to 60° C. and/or increased thermal denaturation temperature, compared to the parent Meripilus giganteus protease. The present invention also relates to polynucleotides encoding the variants; nucleic acid constructs, vectors, and host cells comprising the polynucleotides; and methods of using the variants.