<p>Catalysts that effectively degrade organic pollutants and exhibit bactericidal properties are highly up-and-compromising for water treatment applications. To overcome the inherent limitation that the rapid recombination of the photogenerated carriers and to extend the practical utility of Bi₂WO₆, a flower-like structure of 7 wt.% Er³⁺-doped Bi₂WO₆ (Er_7%-Bi₂WO₆) capable of oxygen vacancy and crystal defect was synthesized using a straightforward hydrothermal method. Under visible light irradiation (λ &gt; 420&#xa0;nm), the Er_7%-Bi₂WO₆ achieved a Rhodamine B (RhB) degradation efficiency of 92% within 80&#xa0;min, significantly surpassing that of pristine Bi₂WO₆. The kinetic rate constant of Er_7%-Bi₂WO₆ was determined to be 0.0288&#xa0;min⁻¹, which is 5.9 times higher than the 0.0049&#xa0;min⁻¹ observed for Bi₂WO₆. Additionally, the bactericidal rate against <i>Escherichia coli</i> after 120&#xa0;min of visible light exposure was 93.9%, nearly twice that of Bi₂WO₆ at 49.8%. Density functional theory calculations and experimental results confirmed that doping with Er³⁺ introduced lower band gap and more photogenerated carriers, enhanced visible light absorption, and ultimately improved the photocatalytic performance. Electron paramagnetic resonance and radical trapping experiments identified h⁺ and ·O₂⁻ as the primary active species generated during the photocatalytic process of Er_7%-Bi₂WO₆. The RhB removal rate remained above 90% after five degradation cycles, and the treatment efficacy on actual water samples was 76%. This study highlights the potential of Er-doped Bi₂WO₆ to enhance both photocatalytic degradation of organic pollutants and bactericidal performance, thereby expanding the application scope of Bi₂WO₆ in water treatment.</p> Graphical Abstract <p></p>