As wireless communication technologies and electronic devices continue to advance quickly, electromagnetic waves (EMWs) have a serious impact on equipment interference and human health. The development of new materials for EMW absorption and shielding is crucial to mitigate electromagnetic (EM) interference. In this study, a unique strategy was implemented for developing a mesoporous polypyrrole/MXene (mPM) composite. The mPM composite was prepared by a molecular synergistic self-assembly method using spherical block copolymer micelles as templating agents to regulate mesopores. The effects of the polypyrrole/MXene ratio and pore size on the EMWs absorption performance of composites were systematically investigated. The mPM composite formed by MXene and polypyrrole exhibits a well-developed porous structure and conductive network, significantly enhancing dielectric loss. The rich mesoporous structures and the multi-layer heterogeneous interfaces can improve the interface polarization, realize multiple reflections, and enhance the EMWs absorption performance of the mPM. The mPM-1 composite, prepared using the PS₁₀₀-b-PEO₁₁₄ template, achieved a reflection loss (RL) of −67.82 dB at an MXene to polypyrrole ratio of 1 with a matching thickness of 1.37 mm. Its effective absorption bandwidth (EBW) was 3.68 GHz (ranging from 14.16 to 17.84 GHz) with a matching thickness of 1.25 mm. It is a reliable way to develop absorbing materials with light, thin, large EBW and high-quality EMWs absorption performance.