In this study, CsPb(ClBr)3 perovskite quantum dot (PQD) structure with different Zn doping ratios was produced by the hot injection method. When the absorption range of the obtained materials was examined between 200 and 800 nm, it was observed that the maximum peak value was reached at 400 nm. When we look at TEM images morphologically, it is observed that the particle sizes obtained were in the range of 2–10 nm. Photocatalysis studies were recorded separately for CsPb(Cl/Br)3 and all Zn-doped CsPb0.87Zn0.13ClBr2 and CsPb0.74Zn0.26ClBr2 for pH: 7 and pH: 10 by evaluating the reduction of methylene blue in UV–vis absorption spectrum. It was observed that the effect increased as the Zn doping increased, especially in the reduction of methylene blue obtained at a pH 10 level. The maximum photocatalytic degradation of 93.98%, 94.99%, and 96.99% were achieved for CsPb(Cl/Br)3, CsPb0.87Zn0.13ClBr2, and CsPb0.74Zn0.26ClBr2, respectively. The Zn-doped CsPb(ClBr)3 QDs and their photocatalysis performances offer a crucial perspective for methylene blue degradation.