The determination of microstructure state is becoming of increasing importance for microelectromechanical system (MEMS) sensors and actuators. Sliding mode-based microtorque estimation for a rotary micromotor, assuming the availability of a MEMS optical monitoring data stream, is presented. The dynamic model of the rotating MEMS system and the electrostatic torque are identified. The technique uses the estimated position signal to approach the actual measured position signal, obtainable through optical monitoring, to simultaneously estimate the microtorque and load torque. The estimated microtorque and load torque are low-pass filtered to eliminate the switching behavior inherent in the sliding-mode estimator. The experimental setup of a lateral comb resonator with optical monitoring is presented and discussed. The simulation results of both electrostatic and load torque estimations are presented, as well as the experimental force estimation of a lateral comb resonator device.