© 2020 Elsevier B.V.We report the structural, elastic, mechanical, electronic and optical properties of Ba2K2Te2O9 (dibarium dipotassium nonaoxidoditellurate) triple perovskite compound by employing generalized gradient approximation (GGA) of first principles density functional theory (DFT) within Perdew-Burke-Ernzerhof (PBE) exchange correlation energy for the first time. This compound shows structural stability and found to be as a direct band gap semiconductor with 2.339 eV band gap energy. Further, elastic compliance constants, stiffness constants and other mechanical properties of Ba2K2Te2O9 were also computed with some optical properties of i.e. the dielectric function, optical conductivity, refractive index, extinction and absorption coefficients. According to Pugh ratio analysis Ba2K2Te2O9 is ductile and displays a more compressible tendency along a - and b -axis and less compressible behavior along the c -axis.