Bamboo-like gallium nitride (GaN) microwires are synthesized via chemical vapor deposition (CVD) to fabricate piezotronic memristors. Defect boundary areas (DBAs) near the bamboo knots produce apparent switching between high and low resistance states upon sweeping of the magnitudes of the biased voltages across the GaN microwire-based devices at room temperature. Furthermore, by coupling the piezoelectric and semiconducting properties in the GaN microwire, the piezotronic effect is introduced to effectively modulate the SET voltages via strain-induced piezoelectric polarizations created at the DBA interface upon mechanical deformation. The experimental results indicate that the device remembered the most recent resistance states when the power is turned off, and the waveform is tunable because of the delayed switching effect. This work provides an alternative approach to the design and modification of memristors based on nanostructured piezoelectric semiconductors using the piezotronic effect.