In this study, carbon black (CB) powder-loaded polyurethane (PU) composites (CB–PU composites) were prepared by melt mixing method with different volume percentages (45, 50, 55, 58 and 61 vol.%) of CB in the PU matrix. The prepared CB–PU composites had been further studied for surface morphology using the field-emission scanning electron microscopy (FESEM) technique. Dielectric properties in terms of real permittivity (𝜀′) and imaginary permittivity (𝜀′′) of the fabricated composites were computed using an Agilent E8364B vector network analyzer in the frequency range of 8–12 GHz (X-band). Dielectric loss factor of the prepared CB–PU composites was computed in terms of the dielectric loss tangent (tan δe = 𝜀′′/𝜀′). Microwave absorbing properties were appraised in terms of the reflection loss (RL) which in turn was calculated for varying thicknesses of the prepared composites from the measured real and imaginary permittivity data. The minimum RL was observed as −20.10 dB for the absorber with a thickness of 2.2 mm and the bandwidth achieved was 1.92 GHz for RL ≤−10 dB. Based on the above results these CB–PU composites have potential use as effective microwave absorbers in 8–12-GHz (X-band) frequency range.In this study, carbon black (CB) powder-loaded polyurethane (PU) composites (CB–PU composites) were prepared by melt mixing method with different volume percentages (45, 50, 55, 58 and 61 vol.%) of CB in the PU matrix. The prepared CB–PU composites had been further studied for surface morphology using the field-emission scanning electron microscopy (FESEM) technique. Dielectric properties in terms of real permittivity (𝜀′) and imaginary permittivity (𝜀′′) of the fabricated composites were computed using an Agilent E8364B vector network analyzer in the frequency range of 8–12 GHz (X-band). Dielectric loss factor of the prepared CB–PU composites was computed in terms of the dielectric loss tangent (tan δe = 𝜀′′/𝜀′). Microwave absorbing properties were appraised in terms of the reflection loss (RL) which in turn was calculated for varying thicknesses of the prepared composites from the measured real and imaginary permittivity data. The minimum RL was observed as −20.10 dB for the absorber with a thickness of 2.2 mm and the bandwidth achieved was 1.92 GHz for RL ≤−10 dB. Based on the above results these CB–PU composites have potential use as effective microwave absorbers in 8–12-GHz (X-band) frequency range.