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BiOBr/Zn2GeO4 heterojunctions decorated by Bi2O3 quantum dots (QDs; named as Bi2O3/BiOBr/Zn2GeO4 hereafter) with intriguing micro/nanostructures have been constructed via a two‐step hydrothermal route. The compositions, phases, and morphologies of Bi2O3/BiOBr/Zn2GeO4 were investigated in detail. The light absorption ability, photocurrent responses, and photocatalytic degradation of methylene blue (MB) experiments were performed to evaluate the photocatalytic activity of the micro/nanoheterostructured Bi2O3/BiOBr/Zn2GeO4, which present a degradation efficiency of 88% after 240 minutes under light irradiation (λ = 300‐600 nm) over 100 mg Bi2O3/BiOBr/Zn2GeO4 in a 100 mL, 4 mg/L MB solution. The photocatalytic performance could be retained for at least four runs, indicating its excellent reusability for the degradation of MB in aqueous solution. It is found that the photodegradation of MB over Bi2O3/BiOBr/Zn2GeO4 is mainly ascribed to a hole oxidation mechanism in combination with a superoxide oxidation process. The high photocatalytic performance of Bi2O3/BiOBr/Zn2GeO4 upon UV light irradiation can be attributed to the effective charge separation and smoothly transferring of the photogenerated charge carriers throughout the heterojunction. The feasible strategy of preparing Bi2O3/BiOBr/Zn2GeO4 ternary composites is also of benefit to fabricate other efficient heterojunction catalysts with specific morphologies and properties.