Display omitted •A 3D porous EMI shielding aerogel of cellulose nanofiber anchored poly(aniline) was fabricated.•Shields exhibited maximum EMI shielding of −32 dB with a high specific EMI SE ∼1667 dB.cm3. g−1.•The porous shields predominantly absorbed (95 %) excess EM radiations with minimal reflection (5 %).•These aerogels readily absorbed undesired EM radiations emitted out from a mobile phone.•The aerogel possess ultra-fast heat dissipation behavior upon high power microwave exposure. Electromagnetic (EM) pollution is ubiquitous and has soared to a great extent in the past few decades. The use of plant sourced cellulose nanofibers to fabricate sustainable and high performance electromagnetic shielding materials is foreseen as a green solution by the electronics industry to address this unseen pollutant. In this view, we report a facile and environmentally benign strategy to synthesize ultra-light and highly conductive aerogels derived from cellulose nanofibers (CNF) decorated with polyaniline (PANI) via a simple in-situ polymerization and subsequent freeze drying process devoid of any volatile organic solvents. The obtained conductive aerogels exhibited density as low as 0.01925 g/cc with a maximum EMI shielding value −32 dB in X band region. These porous shields demonstrated strong microwave absorption behavior (95 %) with minimal reflection (5 %) coupled with high specific EMI SE value ∼1667 dB.cm3. g−1 which make these aerogels a potential candidate for use in telecommunication, military and defense applications.