The invention concerns a catalyst comprising at least one zeolite with structure type MTW, a matrix, at least one metal from group VIII of the periodic classification of the elements, said catalyst having a mesopore volume increased by at least 10% compared with its initial mesopore volume, which is generally in the range 0.55 to 0.75 mL/g, at the end of a treatment with steam at a partial pressure in the range 0.01 to 0.07 MPa and at a temperature in the range 300° C. to 400° C. for at least 0.5 hour. The invention concerns the process for the preparation of said catalyst as well as an isomerization process employing said catalyst.