We report on the synthesis of three-dimensional (3D) hierarchical PbWO₄ microstructures by an oil-in-water microemulsion-mediated route. As-prepared PbWO₄ samples are characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. A possible three-step growth mechanism of PbWO₄, in which initial nucleation, self-assembly (oriented aggregation), and subsequent crystal growth (Ostwald ripening) are involved, is proposed to explain the formation of PbWO₄ microstructures based on observations of a time-dependent morphology evolution process. The approach is facile, environmentally friendly, and provides a new strategy in the use of microemulsion systems for material design and processing. The oil-in-water microemulsion technique presented here offers promising microstructured media for the synthesis of other inorganic materials with complex 3D architectures and unique morphologies and properties.