Pharmaceutical pollutants introduce highly intricate compounds into the environment due to extensive structural and functional alterations resulting in adverse health effects on organisms. Herein, a novel nanocomposite is designed comprising Cu‐doped BiOBr nanoflakes and g‐C3N4 to form a dual absorber based on the organic‐inorganic electronic interface for photocatalytic degradation of tetracycline (TC). With incorporating Cu in BiOBr and compositing with g‐C3N4, the band gap decreased from 2.74 eV to 2.36 eV for BiOBr:Cu/g‐C3N4, and also light harvesting ability increased. The investigation into the degradation rate considered factors such as pH, TC concentration, photocatalyst dosage, and irradiation time, resulting in a TC degradation efficiency of 98 % within 60 min. In the prepared nanocomposite, photo‐generated electrons of BiOBr can recombine via Cu atoms as a mediator with holes in the valence band of g‐C3N4 due to their band structure position which leads to improved electron/hole separation and enhanced photocatalytic activity. The predominant active species involved in the degradation process were found to be superoxide radicals. Additionally, the photocatalyst exhibited excellent stability, retaining 88 % of its photocatalytic activity after four cycles.