We have demonstrated a highly ordered porous carbon (HOPC) as an effective electromagnetic absorber. The unique porous structures allow HOPC to possess high surface area and establish effective three-dimensional (3D) conductive interconnections at very low filler loading, which is responsible for effective electrical loss in term of dissipating the induced current in the corresponding wax composites. Owing to the 3D porous frame, the wax composites with 1 and 5 wt% HOPC have shown effective bandwidth ~ 2 and ~4.5 GHz, respectively, which is considerably competitive to the performance found in the carbon nanotube- (CNT) and graphene-based composites of much higher filler loadings. Such concept based on porous absorbers demonstrates more advantages in the fabrication of lightweight microwave-absorbing materials. Furthermore, the composite with 20 wt% HOPC has exhibited highly effective electromagnetic shielding performance up to 50 dB, which competes well with what has already been achieved in the composites embedded with CNTs and graphene. The fundamental mechanism based on electrical conductivity and complex impedance suggests specific strategies in the achievement of high-performance composites for electromagnetic attenuation and shielding.