A novel mechanical antialiasing interferometric fiber-optic hydrophone with a fourth-order acoustic low-pass filter has been fabricated and demonstrated for the first time to the best of our knowledge. The low-frequency lumped parameters model of the hydrophone is constructed based on the theories of an electroacoustic analogy, and the acoustic performance is predicted by the circuit analysis methods. The measured low-frequency response is very flat, and the acoustic sensitivity is about $-140\mathrm{dB}$ with regard to $1\mathrm{rad}∕\mathrm{\mu }\mathrm{Pa}$ . The system has two measured resonant frequencies, i.e., 850 and $4000\mathrm{Hz}$ , which is in agreement with the simulation results. It is expected that this new type of fiber-optic hydrophone will become an important class of sensors used to eliminate the aliasing in future sonar systems.