Phase change materials (PCM) with enhanced thermal conductivity and electromagnetic interference (EMI) shielding properties are vital for applications in electronic devices, energy storage, and aerospace. However, achieving a synergistic improvement in both thermal and EMI shielding performance remains a significant challenge. This study presents the development of phase change composites reinforced with 3D Ag foam and short carbon fibers (SCF) to address this challenge. Ag@SCF/ PCM composites were fabricated using a vacuum-assisted impregnation and curing process. Polyethylene glycol and epoxy resin formed the PCM matrix, while SCF and Ag foam created a dual-scale interpenetrating network to provide channels for phonon and electron transmission. The dual-scale network significantly improves thermal conductivity (2.24 W/m·K) and EMI shielding (69.7 dB), while maintaining latent heat storage (melting: 71.5 J/g, freezing: 68.7 J/g). These multifunctional properties make Ag@SCF/PCM composites promising candidates for applications requiring simultaneous thermal management and electromagnetic performance optimization.