A high surface, magnetic Fe 3 O 4 @mesoporouspolyaniline core-shell nanocomposite was synthesized from magnetic iron oxide (Fe 3 O 4 ) nanoparticles and mesoporouspolyaniline (mPANI). The novel porous magnetic Fe 3 O 4 was obtained by solvothermal method under sealed pressure reactor at high temperature to achieve high surface area. The mesoporouspolyaniline shell was synthesized by in situ surface polymerization onto porous magnetic Fe 3 O 4 in the presence of polyvinylpyrrolidone (PVP) and sodium dodecylbenzenesulfonate (SDBS), as a linker and structure-directing agent, through 'blackberry nanostructures' assembly. The material composition, stoichiometric ratio and reaction conditions play vital roles in the synthesis of these nanostructures as confirmed by variety of characterization techniques. The role of the mesoporouspolyaniline shell is to stabilize the porous magnetic Fe 3 O 4 nanoparticles, and provide direct access to the core Fe 3 O 4 nanoparticles. The catalytic activity of magnetic Fe 3 O 4 @mesoporousPANI nanocomposite was evaluated in the cross-coupling of aryl chlorides and phenols.