The coupling effect of an electric field with a mechanical deformation makes piezoelectric materials feasible for sensing or actuating functions in structural applications. In a self-sensing actuator system, a single piece of piezoelectric element can be used as both sensor and actuator simultaneously. This technique achieves a truly sensor-actuator collocation and reduces the weight of the structural system as compared to the structure with separate sensor and actuator. However, the self-sensing configuration inherently contains a feedforward dynamics. In order to achieve the self-sensing actuation, the feedforward signal due to the control input must be separated so that the sensing signal is only induced from the mechanical response. The feedforward dynamics is related to the equivalent capacitance of the piezoelectric element, which is subject to change in the ambience. In addition, due to the relatively high amplitudes of the control signal to the mechanical response, small variation of the capacitance would corrupt the sensing voltage. For closed loop applications, this corruption would degrade the system performance or lead it to unstable. In this paper, a self-tuning adaptive algorithm is proposed to compensate for the capacitance variation. Subject to temperature variation, a cantilever beam bonded with a single piezoelectric patch is implemented to demonstrate the effectiveness of the self-sensing actuation. The proposed adaptive algorithm is used to separate the mechanical signal from the total response. Concurrently, control input is generated based on the compensated sensing voltage to actively suppress the beam vibration.