We experimentally demonstrate the workings of a cadmium sulfide/zinc sulfide core–shell nanoparticle-based microwave filter taking advantage of the planar microstrip filter design. The complex permittivity profile shows that the nonlinear dielectric switching remains both reversible and stable for all the cycles that correspond to second-order phase transition. The return loss, transmission loss, and phase shift response show accurate function of the novel as-designed filter across the wide frequency range of 500 MHz to 20 GHz. A notch generated at 11.85 GHz with a rejection level of −50.14 dB confirms the design of the microwave notch filter. A transmission dip appearing at 11.85 GHz is induced by Mie resonance. The observed phase shift of 178.19° at 9.51 GHz confirms the microwave notch generation. This as-designed compact and structurally simple notch filter is capable of wide frequency tuning along with sharp notch generation, paving its possible application as a microwave photonic filter in biomedical systems.