A method and a monitoring unit for monitoring an air pressure in a tire of a motor vehicle register a measured value of the air pressure in the tire. The current and/or future distance of the motor vehicle relative to a service station and/or an operating situation of the motor vehicle associated with a service process is then determined. An alarm signal is only then output if the measured value does not reach a predefinable threshold value and one or both of the conditions applies: the current or future distance of the motor vehicle relative to a service station does not reach a predefinable threshold value, the registered operating situation corresponds to a predefinable operating situation.