We report recent progresses on optical fiber photothermal interferometry for high sensitivity gas and liquid sensing. The basics of photothermal phase modulation with contentiously wavelength/intensity modulated and pulsed pump sources are described, and various interferometric probe configurations for phase detection are discussed. The all fiber configurations operated at the near infrared wavelengths would enable compact and cost-effective sensors with capability of remote detection, multiplexing and sensor networking, which could be used for a range of high performance applications in environmental, medical and safety monitoring.