Recently, Organometallic halide based perovskites have emanated as an auspicious candidate as a solar cell absorber layer. In this article, we have explored the fundamental properties such as structural, electronic, optical, elastic, and thermoelectric parameters of CH(3)NH(3)PbBr(3)through first-principles calculations, because it has accomplished the entire criterion to use in photovoltaic and thermoelectric applications. We have used full-potential linearized augmented plane wave method (FP-LAPW) within DFT and implemented in Wien2k. The generalized gradient approximation (GGA) parameterized by Wu-Cohen (WC) has been used to optimize the lattice parameter, while for band gap calculations different exchange-correlation potentials (LDA/GGA) have been used. The band gap up to 2.26 eV has been achieved by doing some appropriate changes in the parameter of TB-mBJ exchange-correlation potential. The nature of band gap is direct and exist at R (0.5 0.5 0.5) symmetry point of the Brillouin zone. All the optical spectral response between 2 and 5 eV is due to the transition of Br 5p with little contribution Pb 5s orbital electrons of VBM to Pb 6p orbitals in CBM and a minor contribution of second band gap components also incorporate. As well as, a high absorption coefficient shows that it may be strongly applied in photovoltaic devices. The orientation of organic cations (CH3NH3)(+)has no considerable impact on the band structure formation. To render a solid foundation about the application in the thermoelectric device up to the high-temperature region, the thermoelectric parameters have been discussed at optimal carrier concentration and definite temperature range. The measurement of elastic constants, B/G and Poisson's ratio indicates the ductile nature of CH3NH3PbBr3. To the best of my knowledge, most of the investigations have been discussed first time for this material.