A catalyst is described which comprises at least one zeolite with channels with openings defined by a ring having 10 oxygen atoms (10 MI), at least one zeolite with at least channels or side pockets with openings defined by a ring having 12 oxygen atoms (12 MR), at least one metal selected from the group constituted by group IIIA and VIIB metals and at least one porous mineral matrix. Said catalyst optionally also contains at least one metal selected from the group constituted by group IVA and VIB metals. The catalyst of the invention is used in a process for the transalkylation of alkylaromatic hydrocarbons such as toluene or benzene and alkylaromatics containing at least 9 carbon atoms.