Hybridizing electrical (carbon nanotube (CNT)) and magnetic (Fe3O4) fillers enables electromagnetic interference (EMI) shielding and electrostatic discharge (ESD) compliance. In this work, we synthesized CNT-graft-Fe3O4 nanoparticles via co-precipitation and incorporated them in a biodegradable PBSA (poly(butylene succinate-co-adipate)) matrix at 0.1-2 vol.%. We investigated the properties of the composites using hydrostatic densimetry, light flash analysis, broadband dielectric spectroscopy, and four-point surface resistivity testing. The composites containing the synthesized nanoparticles showed a higher volume percolation threshold and a lower surface percolation threshold, while displaying additional ferrimagnetism. Thus, the investigated composites can be used in ESD compliant packaging at low filler loadings and show potential for EMI shielding applications in the defence sector.