This paper presents a novel application of a flexible piezoelectric film sensor to non-invasive fault diagnosis of industrial pipe systems. This sensor is made of oriented aluminum nitride (AIN) thin film, and the total thickness is less than 40 μm. Flexibility of this sensor facilitates installing to surfaces of pipes. Using this sensor, pressure pulsation in pipe systems and vibration of pipe walls can be measured. From the experimental results, components corresponding to the pressure pulsation and the fluid induced vibration motions were recognized as the low-order modes of the power spectra. Then, a fault diagnosis method is developed with these features. Experiments of blockage detection were conducted using a test pipe system. Validation of the proposed method is confirmed through the experiments.