The influence of heavy atom incorporation (in this case, tungsten, W) into scandium nitride is examined to assess its impact on the electronic structure and associated thermoelectric properties. Incorporating W, with its 5d valence electrons, is expected to shift the Fermi level into the conduction band. A solid solution of Sc1−x​Wx​Ny​ system is also expected to form as ScN exhibits the largest unit cell among the early 3d transition metal nitrides. However, phase separation is initiated at x = 0.10 and results in Sc- and W-rich regions occurring through conventional nucleation and growth. High-temperature nitrogen substoichiometry (at ∼800 °C) and formation of secondary phase is governed by inducing N vacancies in the crystal system. The N/W ratio alters the occupancy of the nonbonding t2g states in the valence band and results in phase instability. The Sc1−x​Wx​Ny​ system is found to be less covalent than a ScN reference sample indicating the presence of ionic and metallic bonds as observed through spectroscopic studies. A unique combination of a metal-like Seebeck coefficient with increased electrical resistivity is found for the Sc1−x​Wx​Ny​ system compared to the ScN reference. This study aims to elucidate the structural, microstructural, and electronic properties of the Sc1-xWxNy system and establishing a correlation with thermoelectric properties, through a combined experimental and theoretical approach.