In the presence of polyvinylpyrrolidone (PVP), three-dimensional (3D) hierarchical nest-like architecture of lanthanum carbonate hydroxide (LaOHCO3) with uniform size is successfully synthesized by a facile hydrothermal process using La(NO3)3 as the starting material. The result indicates that LaOHCO3 microspheres are constructed layer-by-layer from a large number of two-dimensional plates, which are composed of numerous nanorods with a length of ∼50 nm. The formation mechanism is discussed on the basis of the result of a time-dependent experiment. It is demonstrated that PVP played an important role in the formation of the hierarchical structure. The room temperature photoluminescence properties of the LaOHCO3 with different morphologies and size are investigated, showing that the nest-like LaOHCO3 exhibits a relative stronger luminescence intensity at 420 nm than the synthesized rod- and apple-like LaOHCO3 samples.