The dependence of the resonant frequency of a piezoelectric microcantilever sensor (PEMS) on electrostatic discharge (ESD), oscillating voltage, dc bias and time was measured from its electrical response. Linear and nonlinear characteristics of the PEMS were analyzed using a lumped parameter model. In particular, the Duffing model-a nonlinear phenomenological model-was adopted to analyze the effects of varying oscillating voltage. The results showed that the ESD can produce a variation in resonant frequency, but can be prevented by earth grounding. In addition, an increase in the oscillating voltage led to a decrease in the resonant frequency owing to the nonlinear spring effect. The resonant frequency exhibited hysteretic behavior with varying dc bias and increased with time. The resonant frequency changed by approximately 18.5 kHz when the oscillating voltage was increased from 0.05 V to 1 V, approximately 9 kHz when the dc bias voltage was increased from 0 V to 20 V and approximately 3.062 kHz over 12 h owing to time drift. The time drift over a period of 30 min remarkably reduced from approximately 0.09% to 0.0049% after a stabilizing time period of approximately 6 h.