This study investigates the mechanical response and wave attenuation performance of an innovative metaconcrete incorporating engineered aggregates composed of solidified/stabilized (S/S) contaminated soil encapsulated within a compliant polymeric coating. The proposed material integrates soil remediation strategies with the design of functional cement-based metamaterials, offering a sustainable solution for vibration and stress-wave mitigation. An experimental campaign was carried out to characterize the elastic properties of the examined stabilized soil, including Young’s modulus and Poisson’s ratio, through compression tests on cylindrical specimens. These experimentally measured properties were subsequently employed to inform both analytical modeling and finite element simulations aimed at predicting the dynamic behavior of the metaconcrete. Dispersion analyses based on Bloch–Floquet theory were performed on a representative unit cell to identify polarization-selective bandgaps associated with local resonance phenomena. The results reveal the presence of a well-defined longitudinal bandgap in the frequency range approximately between 6.5 and 7.5 kHz. A strong agreement is observed between analytical predictions and FEM-based dispersion curves, confirming the robustness of the adopted multiscale modeling framework. The numerical results further highlight the role of local resonance in promoting energy localization within the compliant coating, leading to a marked reduction in longitudinal wave propagation. Overall, the findings demonstrate that stabilized contaminated soils, when properly encapsulated, can be effectively repurposed as resonant inclusions in metaconcrete, combining environmental sustainability with advanced wave attenuation capabilities. The proposed metaconcrete formulation shows significant potential for applications in vibration mitigation, acoustic insulation, seismic shielding, and blast-resistant structural systems.