A method is provided for detecting a leak in a crankcase breather of an internal combustion engine, in which a cavity of a crankcase is connected in a gas conducting manner to a fresh air section of the internal combustion engine. A pressure sensor is provided for measuring a pressure in the cavity. An electronic control unit is provided for evaluating the signals of the pressure sensor. The method includes: measuring of a gas pressure by way of the pressure sensor in the crankcase breather system at a defined rotational speed and load of the internal combustion engine, comparing an actual pressure value with a setpoint pressure value, detecting a leak if the setpoint pressure value is exceeded. As a result of the method, an air flow meter can be dispensed with and a satisfactory separation effect is produced between a satisfactory system and a defective system.