This paper outlines the design and characterization of a setup used to measure the stiffness of microcantilevers and other small mechanical devices. Due to the simplicity of fabrication, microcantilevers are used as the basis for a variety of mechanical sensor designs. In a range of applications, knowledge of the stiffness of microcantilevers is essential for the accurate calibration of the sensors in which they are used. Stiffness is most commonly identified through measurement of the microcantilever’s resonance frequency, which is applied to an empirically derived model. This paper uses a icroelectromechanical system (MEMS)-based force sensor to measure the forces produced by a microcantilever when deformed and a piezoelectric tubebased nanopositioner to displace the microcantilever. A method of calibrating the force sensor is presented that takes advantage of the lumped nature of the mechanical system and the nonlinearity of MEMS electrostatic drives.