This study explores the development of multifunctional electromagnetic (EM) devices using MXene/TiO₂ hybrids, which exhibit tunable conduction loss and polarization relaxation through in situ atomic reconstruction engineering. The MXene/TiO₂ hybrids demonstrate adjustable spectral responses across GHz, infrared, and visible-light spectrums. Several EM devices are constructed based on these materials, including an antenna array, an ultra-wideband bandpass filter, and an infrared stealth device. The antenna array shows excellent EM energy harvesting in multiple microwave bands, with |S₁₁| up to −63.2 dB and tunability via bending. The bandpass filter has a passband of about 5.4 GHz and effectively suppresses EM signal transmission in the stopband. The infrared stealth device has an emissivity of less than 0.2 in the infrared spectrum at wavelengths of 6–14 μm. This work highlights the potential of MXene/TiO₂ hybrids in designing multifunctional, multi-spectrum EM devices for applications in EM protection, wireless communication, and information transmission.This study explores the development of multifunctional electromagnetic (EM) devices using MXene/TiO₂ hybrids, which exhibit tunable conduction loss and polarization relaxation through in situ atomic reconstruction engineering. The MXene/TiO₂ hybrids demonstrate adjustable spectral responses across GHz, infrared, and visible-light spectrums. Several EM devices are constructed based on these materials, including an antenna array, an ultra-wideband bandpass filter, and an infrared stealth device. The antenna array shows excellent EM energy harvesting in multiple microwave bands, with |S₁₁| up to −63.2 dB and tunability via bending. The bandpass filter has a passband of about 5.4 GHz and effectively suppresses EM signal transmission in the stopband. The infrared stealth device has an emissivity of less than 0.2 in the infrared spectrum at wavelengths of 6–14 μm. This work highlights the potential of MXene/TiO₂ hybrids in designing multifunctional, multi-spectrum EM devices for applications in EM protection, wireless communication, and information transmission.