In the present era, the advanced technology demands for the fabrication of light weight and compressible high performance electromagnetic interference (EMI) shielding materials for adaptable shielding application in the area of modern electronic gadgets and telecommunication devices. This study highlights facile fabrication of such lightweight compressible porous polydimethylsiloxane (PDMS)/FRS [Ferrous ferric oxide (Fe3O4) decorated reduced graphene oxide (RGO)/single wall carbon nanohorn (SWCNH)] composite for tunable EMI shielding applications. The Fe powder used to reduce GO, was decorated on the SWCNH and RGO as Fe3O4 during the in situ reaction. FRS dispersed PDMS was allowed to soak and cured in a sugar cube, followed by leaching out of the sugar to obtain highly porous network structure with lightweight and compressible PDMS/FRS composite. The composite possessed an absorption-dominated good comprehensive EMI shielding performance, possibly due to both conductive dissipation and multiple reflections and scattering of EM waves by the inside 3D conductive RGO-SWCNH network with ferromagnetic Fe3O4 nanoparticles. The measurement of attenuation constant and loss tangent describe the absorption property of the composite. The shielding performance of the composite could be simply adjusted owing to its' pressure induced compressible property, applicable as smart tunable EMI shielding material.