The local-resonance bandgap performance of piezoelectric metastructures could be deteriorated by the inherent resistance existing in the piezoelectric patches and the inductors of shunting circuits. In this article, we propose to use negative-resistance circuits to cancel the inherent electrical resistance and therefore enhance vibration reduction performance in the bandgap. The physical model of the piezoelectric metastructure with negative-resistance shunting circuits is firstly illustrated, followed by analyzing its wave dispersion relations and frequency response functions. The enhanced bandgap performance of the piezoelectric metastructure facilitated by negative-resistance circuits is verified with the analytical results. Last, an experimental setup of the piezoelectric metastructure is built. The experimental results demonstrate that the vibration suppression performance in the bandgap is significantly increased by using negative-resistance circuits, and a higher value of negative resistance could lead to larger vibration reduction. Overall, the results of this article provide a novel means to enhance the local-resonance bandgap performance of piezoelectric metastructures.