The invention relates to a fuel filter (10), particularly for diesel fuels, which comprises a housing (11) and a filter medium (12). The filter medium (12) is arranged in the housing by means of a filter medium holder (24) which has a ventilation bore (25). Gases which collect in the upper area of the fuel filter can pass from the untreated space (21) through the ventilation bore (25) to the treated space (22). In order to prevent contaminants from passing out of the fuel filter (10) through the treated fuel outlet (18) and damaging downstream components, a treatment medium (26) which holds back such contaminants is provided.