I–VII semiconductors, well-known for their strong luminescence in the visible region of the spectrum, have become promising for solid-state optoelectronics because inefficient light emission may be engineered/tailored by manipulating electronic bandgaps. Herein, we conclusively reveal electric-field-induced controlled engineering/modulation of structural, electronic and optical properties of CuBr via plane-wave basis set and pseudopotentials (pp) using generalized gradient approximation (GGA). We observed that the electric field (E) on CuBr causes enhancement (0.58 at 0.0 V Å⁻¹, 1.58 at 0.05 V Å⁻¹, 1.27 at −0.05 V Å⁻¹, to 1.63 at 0.1 V Å⁻¹ and −0.1 V Å⁻¹, 280% increase) and triggers modulation (0.78 at 0.5 V Å⁻¹) in the electronic bandgap, leading to a shift in behavior from semiconduction to conduction. Partial density of states (PDOS), charge density and electron localization function (ELF) reveal that electric field (E) causes a major shift and leads to Cu-1d, Br-2p, Cu-2s, Cu-3p, and Br-1s orbital contributions in valence and Cu-3p, Cu-2s and Br-2p, Cu-1d and Br-1s conduction bands. We observe the control/shift in chemical reactivity and electronic stability by tuning/tailoring the energy gap between the HOMO and LUMO states, such as an increase in the electric field from 0.0 V Å⁻¹ → 0.05 V Å⁻¹ → 0.1 V Å⁻¹ causes an increase in energy gap (0.78 eV, 0.93 and 0.96 eV), leading to electronic stability and less chemical reactivity and vice versa for further increase in the electric field. Optical reflectivity, refractive index, extinction coefficient, and real and imaginary parts of dielectric and dielectric constants under the applied electric field confirm the controlled optoelectronic modulation. This study offers valuable insights into the fascinating photophysical properties of CuBr via an applied electric field and provides prospects for broad-ranging applications.