A highly sensitive microbend horizontal fiber-optic accelerometer has been designed, built, and tested. This particular model is aimed at deployment in seismological research where minute accelerations must be detected. The device uses a cantilever beam and the compliance of an optical fiber mounted between deforming teeth to act as the springs in the accelerometer's spring-mass system. Acceleration is detected by sensing the movement of the mass relative to the case through the changes in the intensity of light propagating through the deformed fiber. Accelerations as small as 5 μg at 1 Hz have been detected with a dynamic range in excess of 90 dB.