The inherent fragility of beam–column joints necessitates the retrofitting of existing reinforced concrete structures. However, the effectiveness of such interventions—especially when synthetic reinforcement is employed—may be limited by brittle failure modes and premature debonding. Non-destructive testing methods, such as the electromechanical impedance (EMI) technique, offer a promising approach for early damage detection and structural assessment. This study investigates the combined application of Carbon Fiber-Reinforced Polymer (C-FRP) rope retrofitting and piezoelectric-based structural health monitoring for real-scale beam–column joints. A novel wireless impedance–admittance monitoring system (WiAMS) is employed to capture the response of externally bonded PZT transducers, enabling damage identification through induced variations in electromechanical impedance of PZT sensors. Experimental results from incremental cyclic loading tests, with up to 5% story drift, demonstrate that the proposed retrofitting scheme significantly enhances the seismic performance of beam–column joints. Furthermore, the PZT-based structural health monitoring system effectively tracks load-induced damage and structural degradation of real-scale beam–column joints in real time. The findings of this study highlight the potential of PZT-based monitoring to evaluate the efficacy and performance of retrofitting schemes. Thus, the integration of smart materials and novel monitoring technologies with advanced retrofitting techniques can enhance the resilience and reliability of existing reinforced concrete structures.