Fast charge-discharge rate and high areal capacitance, along with high mechanically stability, are the pre-requisites for flexible supercapacitors to power flexible electronic devices. In this paper, we have used three-dimensional polyacrylonitrile graphite foam as flexible current collector for electro-deposition of polyaniline (PANI) nanowires. The graphite foam with PANI was then used to fabricate symmetric supercapacitor. The fabricated supercapacitor in the three-electrode system shows a high specific capacitance (C-sp) of 357 F.g(-1) and areal capacitance (C-areal) of 7142 mF.cm(-2) in 1 M H2SO4 at current density of 80 mA.cm(-2), while using two-electrode system, it shows C-sp of 256 F.g(-1) and C-areal of 5120 mF.cm(-2) in 1 M H2SO4 at current density of 100 mA.cm(-2). The current density of 100 mA.cm(-2) is up to 10 folds higher than reported current densities of many PANI-based supercapacitors. The high capacitance can be attributed to the spongy network of PANI-NWs on three-dimensional graphite surface which provides an easy path for electrolyte ions in active electrode materials. The developed supercapacitor shows specific energy of 64.8 Whkg(-1) and a specific power of 6.1 kWkg(-1) with a marginally decrease of 1.6% in C-sp after 1000(th) cycles, along with coulombic efficiency retention of 87% in polyvinyl alcohol/H2SO4 gel electrolyte. This flexible supercapacitor exhibits great potential for energy storage application.