We report a successful synthesis of Mesoporous BN (MBN) powder through a facile one-pot synthesis strategy. In this respect, laboratory made block copolymer, polystyrene-b-poly(ethylene oxide) (PS-b-PEO) was used as structure directing agent and ammonia borane was used as BN precursor, respectively. Various characterization techniques such as X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM) and N-2 sorption analysis were used to characterize different properties of the synthesized MBN powder. The formation of turbostratic boron nitride with wormlike pores (20 nm) was confirmed by XRD and TEM results. N-2 sorption analysis of the obtained MBN sample exhibited a high specific surface area of 326 m(2) g(-1) and a pore volume of 0.5 m(3) g(-1).