A MEMS accelerometer includes proof masses that move in-phase in response to a sensed linear acceleration. Self-test drive circuitry imparts an out-of-phase movement onto the proof masses. The motion of the proof masses in response to the linear acceleration and the self-test movement is sensed as a sense signal on common sense electrodes. Processing circuitry extracts from a linear acceleration signal corresponding to the in-phase movement due to linear acceleration and a self-test signal corresponding to the out-of-phase movement due to the self-test drive signal.