<p>With the rapid increase in electromagnetic wave (EMW) pollution, developing high-performance microwave-absorbing materials has become a critical priority. However, achieving effective absorbers with advanced structural properties and optimized multi-component compositions remains challenging. In this research, strong acids were used to surface-modify multi-walled carbon nanotubes (MWCNTs), oxidizing and yielding carboxyl groups on the surface. In situ polymerization applied to the multi-walled carbon nanotubes using a seeding method yielded the coating of polyaniline (PANI) on the MWCNTs uniformly. NiFe₂O₄ nanoparticles (NF NPs) were deposited on the polymerized MWCNT via a co-precipitation method. The particles were heat treated for 10 h at 230 °C to yield crystalline particles. In this research, <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\({\rm{MWCNTs@PANI@NF}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="normal">MWCNTs@PANI@NF</mi> </math></EquationSource> </InlineEquation> Nanocomposites (NCs) were synthesized with three different weight ratios of <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\({\rm{polypyrrole}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="normal">polypyrrole</mi> </math></EquationSource> </InlineEquation> <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(({\rm{PPy}})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>(</mo> <mi mathvariant="normal">PPy</mi> <mo>)</mo> </mrow> </math></EquationSource> </InlineEquation> : 20%, 40%, and 60%. Microscopic examinations showed that the NPs were evenly distributed across the nanotubes’ surface. TEM images determined the average size of the spherical NPs to be approximately 8.25 nm. VSM tests confirmed the ferromagnetic behavior of the samples after the heat treatment process, with a gradual decrease in saturation magnetization observed as the <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\({\rm{PPy}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="normal">PPy</mi> </math></EquationSource> </InlineEquation> weight ratio increased. To evaluate EMW absorption (EMWA) capabilities, the samples were tested in the X and Ku bands. The NC₃ sample recorded the highest reflection loss (RL) of -21.19 dB under the X band at d = 3.24 mm, and the same sample recorded RL values of -13.49 dB and -11.07 dB under the Ku band, both at the same thickness. These results demonstrated that <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\({\rm{MWCNTs@PANI@NF@PPy}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="normal">MWCNTs@PANI@NF@PPy</mi> </math></EquationSource> </InlineEquation> NCs, despite lower magnetization, showed superior EMW absorption performance compared to homogeneous composites. Due to advantages such as low weight, scalability for mass production, high stability, and recyclability, these NCs are recognized as innovative candidates for applications in microwave-absorbing materials.</p> Graphical Abstract <p></p>