We present a comparative study on the structural, electronic, elastic, and thermoelectric properties of the cubic inverse-perovskites A(3)OX (where A = Li, Na, K and X = Cl, Br, I) by density functional theory (DFT). The cohesive, formation, and elastic properties analysis indicates that all studied materials are chemically, thermodynamically, and mechanically stable. Electronic properties reveal that all the inverse A(3)OX perovskite are direct bandgap semiconductors except Li3OCl and Li3OBr with ionic nature which is confirmed by electron localization function (ELF) analysis. We have also calculated Debye temperature (Theta(D)) and Gruneisen parameter (gamma) to determine the lattice thermal conductivity for all the A(3)OX materials. Furthermore, thermoelectric (TE) properties are explored by calculating the Seebeck coefficient (S), electronic thermal conductivity, power factor (PF), electrical conductivity (sigma/tau), lattice thermal conductivity, and ZT value. Our investigated A(3)OX inverse-perovskites provide a fertile base that can improve the overall TE performance for TE applications and green energy production.