<p>Rare-earth ternary materials have distinctive features such as excellent optical response and exceptional stability in their thermoelectric nature. The present study investigates the complex interaction between the structural, optoelectronic, and thermoelectric properties of the novel NdXF (X = S, Se) ternary semiconductors by employing the density functional theory. NdSF and NdSeF have predicted band gaps of 1.79&#xa0;eV and 1.50&#xa0;eV, respectively. The p states of both chalcogens play an important role in the bonding properties and electronic structure of these materials. These materials displayed metallic behavior, as evidenced by the negative values of ε₁^xx(ω) and ε₁^zz(ω). The reflectivity spectra increase gradually up to 4.0&#xa0;eV, showing that these materials absorb more light as photon energy increases. The thermoelectric properties were also investigated, such as the thermal conductivity, Figure of Merit, electrical conductivity, and Seebeck coefficient. The current study could demonstrate its potential application in advanced optoelectronic devices, paving the path for a wide variety of innovations.</p>