Currently, the development of low-reflection electromagnetic interference (EMI) shielding composite materials for mitigating secondary electromagnetic wave pollution has become a major research focus. However, achieving thinness, high toughness, low reflectivity, and multifunctionality in flexible EMI shielding films remains a challenge. To address this issue, this study introduces a “magnetic–electric” Janus structure EMI shielding composite film composed of MXene nanosheets, carbonized ZIF-67 (CZIF67) nanoparticles and aramid nanofibers (ANF), balancing thinness, high toughness, low reflectivity, and multifunctionality. As a result, the MXene/ANF-CZIF67/ANF-4 (MACA-4) sample exhibits high tensile strength (110.0 ± 7.0 MPa), large strain tolerance (21%), and superior toughness (14.9 ± 0.9 MJ·m⁻³), reflecting the stress dispersion effect of the three-dimensional (3D) network structure of ANF and the strengthening effect of hydrogen bonding. The sample exhibits excellent flexibility, resistance to rubbing and folding. Even with a thickness of only 80 μm, the MACA-4 film exhibits a reflection performance (SE_R) as low as 4.3 to 4.5 dB in the 8.2 to 9.6 GHz band and the SE_T in the X-band reaches 44.8 dB. In addition, the superior conductivity of the MXene/ANF layer and the localized surface plasmon resonance effect give the MACA composite films excellent electrothermal conversion capabilities. Surprisingly, the sample also exhibited excellent infrared stealth and fire alarm properties. This work offers valuable guidance on the fabrication of ultra-thin flexible EMI shielding composites and provides an important scientific basis for the design and application of efficient EMI shielding materials.