Abstract: There has recently been a fundamental need to develop high efficiency microwave absorbers to reduce electro-magnetic pollution. It is often very difficult to obtain superior absorption with only one material, so we have explored composites using fillers of activated carbon derived from biological material (oleaster seeds) and resin (apricot tree gum) with Fe₃O₄ in a paraffin wax matrix to improve the dielectric properties and achieve a high specific surface area. A 1 mm thick layer of a Fe₃O₄ + resin (FEOR), with the magnetic nanoparticles anchored to the gum, resulted in a reflection loss of −71.09 dB. We compared this with the results for composites using a filler of Fe₃O₄ + activated carbon, and one with a three-component filler of Fe₃O₄ + activated carbon + resin which had a very porous structure that had a direct effect on the surface polarization. However, the FEOR sample had near-ideal impedance matching, close to 1, which resulted in high absorption performance. In addition, the presence of defects improves microwave attenuation by dipole polarization and charge carrier trapping. This work suggests the use of new types of biomaterials to increase microwave absorption.