This paper presents a novel adaptive sliding mode control with a sliding mode observer for a microelectromechanical system (MEMS) gyroscope. The proposed adaptive sliding mode controller with a sliding mode observer can estimate the unmeasured velocities, angular velocity, and damping and stiffness coefficients of the gyroscope in the presence of parameter variations and external disturbance. A novel adaptive sliding mode controller with a proportional and integral sliding surface is derived and the stability condition of the closed-loop feedback system is established. Simulation results demonstrate the effectiveness of the proposed adaptive sliding mode controller with sliding mode observer.