The aim of this work is a comprehensive study of the structural and electronic properties of the trirutile compound FeSb₂O₆. The quantum DFT approximation used for this research was applied to iron antimonate oxide, which has a well-defined trirutile structure with the space group P42/mnm (136). It crystallizes in a tetragonal lattice, featuring unit-cell parameters of a = 0.466 nm and c = 0.924 nm. The structural characteristics of a material can be thoroughly investigated without the need for physical measurements by employing optimized first-principles computational methods. In this case, the CASTEP code, integrated within the Material Studio software suite, was utilized based on a pseudo-potential plane-wave approach. In this study, the geometrical optimization of FeSb₂O₆ was conducted using a semi-local generalized gradient approximation (GGA), specifically employing the Perdew–Burke–Ernzerhof (PBE) exchange–correlation functional. Additional functionals used include the PBE for solids (PBESOL), Perdew-Wang91 (PW91), the revised PBE (RPBE), and the local density approximation (LDA-CAPZ). After optimization, both the band gap values and the density of states (DOS) of FeSb₂O₆ were calculated to gain deeper insight into its electronic properties. The electronic properties of FeSb₂O₆ were determined by examining its electronic band structure and DOS, establishing it as a narrow-gap semiconductor with a direct band gap, making it promising for potential electronic applications.