In this study, we report high-performance EMI shielding composites incorporating directionally aligned non-oxidized graphene flakes (NOGF) within a polydimethylsiloxane (PDMS) matrix. NOGF was obtained by exfoliating graphite intercalation compounds without oxidation, preserving its graphitic structure. Unidirectional freeze-casting method was used to form aligned NOGF aerogels, which were infiltrated with PDMS to create lightweight, flexible composites. The NOGF/PDMS composite achieved a maximum shielding effectiveness (SE) of 54.2 dB at 2.1 mm, surpassing reduced graphene oxide (rGO)/PDMS (31.4 dB at 2.5 mm). The SE was direction-dependent, with longitudinal samples performing better than transverse ones. The composites also showed improved tensile strength, Young's modulus and toughness due to efficient load transfer and enhanced filler-matrix interaction from the defect-suppressed NOGF. These results highlight the potential of low-content graphene composites for EMI shielding.