Owing to immense potential applications, in-plane anisotropy has attracted tremendous interest in the mechanical, optical, and thermal properties of two-dimensional (2D) materials for the development of the novel devices. In this work, we used the first-principle calculations to investigate the electronic structure, optical, and thermodynamic properties of the monolayer Sn 0.5 Ge 0.5 Se nanosheet. The nanosheet comprises an armchair and zigzag configurations established towards the X and Y orientation. Band structure and density of the states reveal that the studied nanosheet is a p-type semiconductor with 1.23 eV band-gap. Band structure and density of the states reveal a p-type semiconductor with 1.23 eV band-gap. We estimated the optical properties in different electric polarization. The optical properties confirm the nanosheet is transparent that used for optoelectronic applications. Thermodynamic properties confirm the stability of the nanosheet at a high temperature. • Electronic, optical, and thermodynamical properties of Sn 0.5 Ge 0.5 Se nanosheet were studied. • Band structure and PDOS confirms a p-type semiconductor with a bandgap of 1.23 eV. • The Se-4p electrons and Sn-5s and 5p electrons are dominating near the Fermi level. • Optical properties were studied in different electric polarization. • Thermodynamic studies reveal the nanosheet is stable at high temperatures.