<p>A facile and industrially scalable dip-coating approach is reported for the fabrication of semi-reticulated melamine formaldehyde (MF) foams reinforced with multi-walled carbon nanotubes (MWNTs), targeting lightweight electromagnetic interference (EMI) shielding applications. The dip-coating process enabled controlled resin impregnation within the open-cell foam structure, preserving a significant portion of porous architecture while simultaneously facilitating the formation of a continuous conductive network along the foam skeleton. The resultant composite foams demonstrate a pronounced increase in electrical conductivity beyond the percolation threshold, which directly translates into a significant enhancement in EMI shielding effectiveness across the X-band frequency range (8.2–12.4&#xa0;GHz). The composite foam containing 4.7 vol.% MWNTs achieves an average total shielding effectiveness (SE_T) of 36.8&#xa0;dB, corresponding to 99.98% attenuation of incident electromagnetic radiation. Moreover, an exceptionally high absolute specific shielding effectiveness (ASSE) of 222.7&#xa0;dB cm²&#xa0;g⁻¹ was achieved. A comparative analysis against solid counterparts with equivalent nanotube loadings revealed that the semi-reticulated foam architecture introduces additional internal interfaces and multiple scattering pathways, leading to absorption-dominated shielding mechanism. The synergistic contributions of interfacial polarization, conductivity loss, and multiple internal reflections are identified as the governing mechanisms underlying the enhanced microwave attenuation. Collectively, these results establish semi-reticulated MWNT–MF foams fabricated via a facile dip-coating method are promising candidates for lightweight, high-performance, and industrially scalable EMI shielding applications.</p> Graphical abstract <p></p>