Abstract In this study, via a simple one‐step method, chiral copper sulfide quantum dots (d/l‐QDs) were prepared using d‐/l‐penicillamine (d‐/l‐Pen). The anisotropy factor of d/l‐QDs was as high as 0.01. The d/l‐QDs can be used as photocatalysts to cleave proteins. Notably, the l‐QDs displayed the highest catalytic performance under left‐circularly polarized light irradiation. Mechanistic investigations indicate the generation of hydroxyl radicals as the reactive species that cause the cutting of proteins.