The invention concerns a process for the preparation of a catalyst based on tungsten intended for hydrotreatment or hydrocracking processes.The invention concerns a process for the preparation of a catalyst for carrying out hydrogenation reactions in hydrotreatment and hydrocracking processes. Said catalyst is prepared from at least one mononuclear precursor compound based on tungsten (W), in its monomeric or dimeric form, having at least one W═O or W—OR bond or at least one W═S or W—SR bond where [R═CxHy where x≧1 and (x−1)≦y≦(2x+1) or R═Si(OR′)3 or R═Si(R′)3 where R′═Cx′Hy′ where x′≧1 and (x′−1)≦y′≦(2x′+1)], optionally at least one Mo precursor and optionally at least one promoter element from group VIII. Said precursors are deposited onto an oxide support which is suitable for the process in which it is used, said catalyst advantageously being sulphurized before being deployed in said process.