The structural, electronic, magnetic, optical and thermoelectric properties of anti-fluorite Cs(2)NbI(6)were investigated using full potential augmented plane wave method of density functional theory. Structurally, Cs(2)NbI(6)was found to be cubic in ground state from values of tolerance factor (1.04) and formation energy (-22.3 eV). While, it's ferromagnetic nature was predicted from volume optimization process. In spin down channel, the compound was explored as indirect band gap (Eg(Gamma-X)= 1.97 eV) semiconductor, while it changes to metallic in upper spin channel. Nb-dand I-pstates were exposed as the main cause of spin dependent electronic nature (half-metallicity). The origin of magnetism in Cs(2)NbI(6)was explained on basis of crystal field theory. The calculated magnetic moment (1.001 mu(B)) was found in reasonable agreement with experimental value. The optimum absorption and optical conductivity spectra in semiconductor state explored Cs(2)NbI(6)as suitable for optoelectronic devices. Furthermore, the transport properties were calculated using BoltzTrap code. The nature of carriers was predicted as n type from negative values of Seebeck coefficients. Where, the figure of merit (ZT) was found to increase up to 0.85 at 900 K. The present work not only explores Cs(2)NbI(6)as potential optoelectronic and thermoelectric material, but can also inspire more experimental research on this important compound.