Bismuth oxybromide (BiOBr) nanosheets with fully exposed {001} and {010} facets are synthesized via a facile hydrothermal method. Significant differences in photocatalytic inactivation towards Escherichia coli K-12 under visible light irradiation are found to be highly dependent on the dominantly exposed facets. In comparison with BiOBr with dominant {010}-facet (B010) nanosheets, BiOBr with dominant {001}-facet (B001) nanosheets exhibit remarkably higher photocatalytic activity in bacterial inactivation. This superior activity is ascribed to the more favorable separation and transfer of photogenerated electron–hole pairs as well as more oxygen vacancies of B001 nanosheets. Due to the faster production and further accumulation of ˙O₂ ⁻ and h⁺ within a short time, the VLD photocatalyst of B001 nanosheets can completely inactivate 10⁷ colony forming unit (CFU) mL⁻¹ (i.e. 7-log reduction) bacterial cells within 2 h; while only 1- and 6.5-log reductions of bacterial cells can be achieved within 2 and 6 h, respectively, by B010 nanosheets due to limited amounts of h⁺ and ˙O₂ ⁻ generated.